bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionic Transport in Aptamer Functionalized Nanochannel Array
Authors: Devarakonda Sivaranjani , Du Pengfei , Ganapathysubramaniam Baskar , Shrotriya Pranav
Published: February 2020

We report theoretical and experimental results of the influence of surface immobilized aptamers on ionic transport through nanochannels. The ionic transport in a polyelectrolyte functionalized nanochannel may be modified either by electrostatic mechanisms that involve changes in double layer formed near the pore walls or through steric hindrance of the surface chains on the transport of solution ions. Arrays of well-defined nanochannels are fabricated using two-step anodization process of aluminum on ITO coated glass substrate. The anodization voltage and electrolyte are chosen to achieve the desired nanochannel radius and distribution. The alumina nanochannels are functionalized with thrombin binding DNA aptamers (TBA) to enable the formation of monomolecular films of polyelectrolytes on the nanochannel surface. The functionalized nanochannel arrays are then exposed to different concentrations of α-thrombin and change in impedance across the nanochannel array are characterized in order to identify the influence of protein/aptamer binding on the ionic conduction in the nanochannels. Both DNA aptamers (specific to thrombin) and α-thrombin are charged species and their interactions produce modulation of surface charges and modify the net ionic conductance across the nanochannel. We also characterized changes in ionic conductance in presence of γ-thrombin, an uncharged protein that has similar physiological structure as α-thrombin but no affinity towards TBA. Ionic and solution transport in the nanochannel is modeled using coupled Poisson-Nernst-Planck equation and Navier-Stokes equations. The conformation and charge density of aptamer monomolecular films on the nanochannel surface was modeled based on molecular dynamics simulation results of aptamer and thrombin/aptamer complexes (Gosai et al., 2016). The predicted changes in ionic conductance are compared to experimental results to identify the influence of electrostatic and steric interactions on the ion transport in polyelectrolyte functionalized nanochannel. The results show that aptamer functionalized alumina nanochannel have potential to be used for the development of disposable and point of care devices by employing relatively facile and inexpensive fabrication methodologies.

Reference:

Gosai, A., Ma, X., Balasubramanian, G., Shrotriya, P., 2016. Electrical Stimulus Controlled Binding/Unbinding of Human Thrombin-Aptamer Complex. Sci. Rep. 6, 37449. doi:10.1038/srep37449
3D Printed Electrodes for Membraneless Electrolyzers
Authors: Bui Justin C , Davis Jonathan T , Cousens Erin Shin , Esposito Daniel V
Published: February 2020

In the past decade, the field of additive manufacturing (3D printing) has grown significantly. New techniques and materials are constantly being explored, and novel applications of these technologies have been a focus of a multitude of recent scientific research. Another field that is experiencing a concurrent trajectory of growth is that of solar fuels, which broadly encompasses technologies that convert solar energy into storable gaseous or liquid fuels. Hydrogen (H2) is an appealing carbon-free fuel, as it can be sustainably produced through water electrolysis with electricity from photovoltaics. Unfortunately, state of the art electrolyzers have prohibitive capital costs and are prone to degradation. Motivated by this challenge, our group seeks to lower capital costs by developing simplified electrolyzer devices which operate without a membrane. One method of realizing such devices is through the utilization of additive manufacturing. In this study, we use additive manufacturing to fabricate flow-through electrodes printed from a conductive graphene-polymer composite filament. The performance of a series of electrodes is evaluated through a combination of electroanalytical measurements and in situ high speed video imaging. This work sets the stage for monolithic electrochemical reactors made entirely by additive manufacturing technologies.
Using Optical Trapping and Surface Energy to Investigate the Interactions between E. coli and Functionalized Substrates
Authors: Beckmann Thomas J. , Danhausen Dany M , Crowder Chuck D , Keleher Jason J.
Published: February 2020

Bacterial infections have been an escalating problem for healthcare facilities, especially those due to multi-drug resistant bacteria. Infections spread in a plethora of ways, particularly through repeated transfers of bacteria among various surfaces. To better understand the process of bacterial transfer, the mechanism of bacteria-surface interaction as well as the affinity of that interaction must be explored. Recent studies suggest that Van der Waals and electrostatic contributions drive the close-proximity interactions between the bacteria and the substrate surface. Understanding the factors that drive bacteria-substrate interactions provides information on bacterial activity such as cell adhesion, death and biofilm formation. To investigate these mechanisms, this research analyzes the viability and affinity associated with the interactions between E. coli and functionalized surfaces via epifluorescence microscopy, optical trapping and surface energy analysis. Epifluorescence microscopy and optical trapping were simultaneously used to monitor cell viability and probe interactions between single E. coli cells and substrate surfaces. Cell death was observed on modified surfaces while unmodified surfaces demonstrated no influence on cell viability. Contact angle measurements were used to quantify the surface energy of E. coli in solution on substrate surfaces. The surface energy of E. coli in solution decreased more rapidly on functionalized substrates than inert surfaces, indicating cell death or biofilm formation.
Metal-Organic Framework Supported on Food Waste-Derived Carbon As an Efficient Bifunctional Catalyst for Oxygen Electrocatalysis
Authors: Wang Hao
Published: February 2020

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are a core pair in many energy storage and conversion systems, such as regenerative fuel cells and rechargeable metal-air batteries. Unfortunately, both reactions possess sluggish kinetics, involving multiple charge-/proton-transfers and oxygen bond breaking (in ORR)/recombining (in OER) processes at the “solid-liquid-gas” triple phase interfaces. Therefore efficient bifunctional catalysts are urgently needed. The most efficient oxygen-relative electrocatalysts are made from precious metal, but there is no a single catalyst based on precious metals that can serve the need for both ORR and OER.

Metal-organic frameworks (MOFs) are porous crystalline materials self-assembled with metal nodes and organic linkers with various compositions, high specific surface areas, tunable pore structures, and easily functionalized. Therefore, MOFs have provided opportunities for advancements in oxygen electrocatalysis. MOFs-based ORR/OER electrocatalysts are generally used in two ways: (1) by self-sacrificing through pyrolysis, and (2) in pristine phases. The former is at the expense of MOFs’ properties, while the latter falls short of meeting the practical target due to the poor conductivity of pristine MOFs, requiring carbon support. Conventional carbon supports are synthesized from fossil fuel precursors with harsh synthetic conditions and high energy consumption. Sustainable carbon materials should be derived from renewable resources (especially agriculture/food waste), and the preparation process should be green, facile and easy to scale up.

Herein, a Co(mIm)2 (mIm=methyl-imidazole) MOF was incorporated with N-doped pomelo-peel-derived carbon (NPC) as a synergistic ORR/OER bifunctional catalyst in an alkaline electrolyte (Fig. 1A). Through rotating disk electrode voltammetry, an optimized composite exhibits an ORR/OER overpotential gap, ΔE (E
OER@10 mAcm-2-E
ORR@-1 mAcm-2), as small as 0.79V (Fig. 1B), putting the catalyst among the best of the reported bifunctional electrocatalysts so far. The catalyst also demonstrated a 4-electron transfer pathway and superior catalytic stability. The Co-N4 ligation in MOF, electrochemical active surface area, and the strong interactions between MOF and support are attributed as the main contributors to the bifunctional catalytic activity. These factors act synergistically, resulting in substantially enhanced bifunctional catalytic activity and stability.

Figure 1
Instability and Degradation Mechanism of Platinum-Group Metal (PGM)-Based Carbon Supported Electrocatalysts in Alkaline Medium
Authors: Lafforgue Clémence , Dubau Laetitia , Maillard Frederic , Chatenet Marian
Published: February 2020

Direct liquid alkaline fuel cells (DLAFC) are considered high-energy density generators and arouse interest because (i) their energy density can be higher than for closed systems like Li-ion batteries, and (ii) they do not suffer from issues related to H2 compression, storage and delivery as for proton-exchange membrane fuel cells (PEMFC). Moreover, electrocatalyst commonly used for PEMFC suffer from a poor durability in operation [1]. In the case of alkaline fuel cells, despite few studies, the common belief supposes a larger stability of electrocatalysts in alkaline medium compared to acidic medium, owing to the better thermodynamic stability of many metals and oxides at high pH, as predicted by Pourbaix [2].

In reality, some recent studies showed that the state-of-the-art carbon-supported platinum nanocatalysts are subjected to severe degradations upon a mild potential cyclic procedure in 0.1 M NaOH at 25°C [3]. The loss of electrochemical surface area (ECSA) reaches 60 % after 150 cycles in the range 0.1 - 1.23 V vs. RHE at 100 mV s-1. Herein, the same degradation procedure has been performed with Pd/C and PtRu/C: non-negligible ECSA loss (ca. 35 %) is monitored for Pd/C, whereas very harsh degradation is noted for PtRu/C.

Identical-location transmission electron microscopy studies (ILTEM) revealed that the main degradation mechanism is, whatever the electrocatalyst, the detachment of the nanoparticles from the carbon substrate (Figure 1 D-E-F). It is suspected that this detachment follows the rupture of the binding between the PGM nanoparticles and the carbon support, triggered by the formation of carbonates originating from PGM-assisted corrosion of the carbon support. The CO-stripping experiments performed in NaOH 0.1 M (Figure 1 A-B-C) confirm that the ability of each electrocatalysts to form CO2 is linked to the observed degradations.

This work was partly supported by an ONR-global grant (project ONR N62909-16-1-2137).

References

[1] L. Dubau, L. Castanheira, F. Maillard et al., WIREs Energy and Environment 2014, 540, 3.

[2] M. Pourbaix, National Association of Corrosion Engineers 1979, 453.

[3] A. Zadick, L. Dubau, N. Sergent, G. Berthomé, M. Chatenet, ACS Catalysis 2015, 4819, 5.

Figure 1
Effect of Fillers on Viscosity and Electrical Conductivity of Glass Composite Sealants
Authors: Baek Sueng-Ho , Park Sung , Lee Jae Chun
Published: February 2020

Development of a reliable sealant or sealing system remains one of the top priorities in planar solid oxide fuel cells (SOFC) technology. Glass matrix composites as sealing materials for SOFCs are known to enable design flexibility, e.g., by control of such properties as viscosity, seal operating temperatures, and visco-elastic properties. The objective of this study was to find suitable fillers for structural strengthening as well as for improving long-term cyclic sealability of the alkali borosilicate glass composite sealants. Alkali ion containing compliant sealing glass was developed by present authors. Two kinds of fillers, Al2O3 and 8 mol % Y2O3-stabilized zirconia (8YSZ), were used up to 15% for the preparation of glass composite sealants. The effects of these fillers and their content on the high temperature viscosities and electrical conductivities of the sealants were investigated. Furthermore, glass composite to STS444 seal assemblies were subjected to thermocycling between 450°C and 750°C. The composition of a glass composite sealant to survive over 12,000 h of consecutive cyclic test was identified. In this presentation, effect of fillers on properties and cyclic sealing behavior of the glass composites will be also discussed.
Metal-Organic-Frameworks-Modified Separator for Lithium–Oxygen Batteries with Long Cycle Life
Authors: Zhang Xiahui , Cha Younghwan , Dong Panpan , Lee Jung-In , Song Min-Kyu
Published: February 2020

Lithium-ion batteries (LIBs) are reaching their theoretical energy limit, but still cannot meet the needs for all-electric vehicles. Owing to their five times higher energy density (~3500 W h/kg) than that of LIBs, lithium–air (Li–O2) batteries have been considered as one of most promising next-generation energy storage devices.1 However, Li–O2 batteries still suffer from several challenges that hinder their practical applications, such as low energy efficiency and poor cycle life.2 Recently, it has been demonstrated that the gradual accumulation of side products due to parasitic reactions can result in the failure of Li–O2 batteries.3 Therefore, the cyclic performance of Li–O2 batteries can be significantly improved by preventing the accumulation of side products.

Metal–organic frameworks (MOFs), a novel type of crystalline porous materials, have been widely studied as adsorbents for gas separation or storage due to their large surface area, high micro-porosity, and chemically unsaturated metal sites.4 Recently, MOFs-modified separators have been reported as molecular sieves to mitigate the shuttling effect of polysulfides in lithium–sulfur batteries.5 Herein, we report a MOFs-modified separator for Li–O2 batteries. In this work, nanocrystalline MOFs are prepared and then coated on a GF/D separator by a facile method. The as-fabricated MOFs-modified separator showed much-improved cycle life up to 200 cycles at a current rate of 125 mA/g, compared to untreated GF/D separator. The mechanism of how MOFs mitigate the accumulation of side products on the cathode will be also discussed in this presentation.

Reference

1 Bruce, P. G., Freunberger, S. A., Hardwick, L. J. & Tarascon, J. M. Li–O2 and Li–S batteries with high energy storage. Nat Mater
11, 19-29, doi:10.1038/nmat3191 (2012).

2 Luntz, A. C. & McCloskey, B. D. Nonaqueous Li–air batteries: a status report. Chem Rev
114, 11721-11750, doi:10.1021/cr500054y (2014).

3 Kim, B. G. et al. Ordered Mesoporous Titanium Nitride as a Promising Carbon-Free Cathode for Aprotic Lithium–Oxygen Batteries. ACS nano
11, 1736-1746 (2017).

4 Furukawa, H., Cordova, K. E., O’Keeffe, M. & Yaghi, O. M. The chemistry and applications of metal-organic frameworks. Science
341, 1230444 (2013).

5 Bai, S., Liu, X., Zhu, K., Wu, S. & Zhou, H. Metal–organic framework-based separator for lithium–sulfur batteries. Nat. Energy
1, 16094 (2016).
Reduced Graphene Oxide As an Advanced Anode for Li-Ion Battery
Authors: Park Jinho , Perini Chris , Navaei Milad , Hankinson John , Lee Byeongyong , West Matt , Vogel Eric M , Lee Seung Woo , Stern Ilan
Published: February 2020

Although graphite is the most commonly used anode material for Li-ion batteries, its low capacity (372 mAh/g) limits the energy storage performance. Recently, graphene has demonstrated great promise as a candidate to replace graphite due to its high power and high energy densities.1-3 Here, we prepared Li-ion battery anodes based on reduced graphene oxide (rGO) powder obtained from an established company and investigated effects of oxygen contents in the rGO on the energy storage properties. The oxygen content of rGO could be controlled by heat-treating the rGO at 500 oC and 800 oC under Ar condition. The O/C atomic ratios from XPS were 0.208, 0.126, and 0.031 for the pristine rGO, the rGO heat-treated at 500 oC (rGO-HT500) and the 800 oC (rGO-HT800), respectively. We employed Dr. Blade method to prepare the electrodes using the pristine and heat-treated rGO. While the loading density of the electrodes were kept in the range of 1.68−1.75 mgrGO/cm2
electrode, the density gradually decreased with the heat-treatment from 0.62 to 0.21 g/cm3. We then fabricated a Li coin-type cell (CR2032) with the rGO electrode in an Ar-filled glovebox. Li metal foil, Celgard 2500 membrane, and 1 M LiPF6 (in EC/DMC) were used as a counter electrode, a separator, and an electrolyte, respectively. For evaluating energy storage performance of the rGO-based electrode, we conducted galvanostatic charge/discharge test at different current densities in the range of 37.2–3720 mA/g. At the current density of 37.2 mA/g, both electrodes based on the pristine rGO and rGO-HT500 showed ~1000 mAh/grGO, which is greatly enhanced capacity by 2−3 folds relative to the theoretical capacity of graphite (Fig. 1). However, the rGO-HT800-based electrode exhibited only showed a capacity of 579 mAh/grGO, indicating the minor oxygen content could contribute to the charge capacity of rGO in the Li-ion battery.

J. Hassoun et al., An advanced lithium-ion battery based on a graphene anode and a lithium iron phosphate cathode. Nano letters
14, 4901-4906 (2014).

G. Wang, X. Shen, J. Yao, J. Park, Graphene nanosheets for enhanced lithium storage in lithium ion batteries. Carbon
47, 2049-2053 (2009).

F. J. Sonia et al., Understanding the Li-storage in few layers graphene with respect to bulk graphite: experimental, analytical and computational study. Journal of Materials Chemistry A
5, 8662-8679 (2017).

Figure 1. (a) Charge/discharge profiles of pristine rGO at difference current densities from 37.5 to 3750 mA/g. (b) Comparison of charge/discharge profiles of pristine and heat-treated rGO electrodes obtained at 37.5 mA/g.

Figure 1
Nitrogen-Doped 3D Graphene-like Carbon Synthesized Using a Zeolite Template As a Metal-Free Oxygen Reduction Electrocatalyst
Authors: Han Seung Won , Ko Seung Hyeon , Kwon Yonghyun , Bang Jisuk , Ryoo Ryong
Published: February 2020

Ordered microporous carbons synthesized using a zeolite template have gained much attention owing to their excellent performances in advanced energy applications, including oxygen reduction reaction, electrical double-layer capacitors, and batteries. Their outstanding performances were attributed to the physicochemical properties of the carbon, such as high surface area of >2000 m2 g-1, large pore volume of >1.0 cm3 g-1
, and high conductivity. The electronic properties of zeolite-templated carbon (ZTC) can be modified through doping with heteroatoms, which can result in a further improvement of its electrochemical activities. The synergistic combination of its structural features and modified electronic properties is expected to enhance the performance of carbon as an electrode material in electrochemical applications. In this regard, we synthesized nitrogen-doped ZTCs using various nitrogen-containing carbon precursors. The synthesis was done with an aid of Ca2+ ion catalysts embedded inside the zeolite framework, following the recently reported approach by our group. The precursors were selected considering the size of the precursor molecule, the strength of carbon-nitrogen bond, and their interactions with Ca2+ ion catalysts. The resultant carbon exhibited high nitrogen content, uniform microporosity, high surface area, and 3D pore structure. Herein, we report the characterization of nitrogen-doped ZTC, and performances of both nitrogen-doped and undoped ZTCs as a metal-free catalyst for oxygen reduction reaction, focusing on the oxygen reduction behavior according to the nitrogen content, nitrogen bonding configurations, and porous texture of the carbon.
CVD Graphene Growth for Redox Reactions to Renewable Energy Applications
Authors: Ion-Ebrasu Daniela , Spinu-Zaulet Adnana , Enache Stanica , Soare Amalia , Carcadea Elena , Enache Adrian , Varlam Mihai
Published: February 2020

In this paper we report on the graphene growth via chemical vapor deposition (CVD) for Oxygen Reduction Reaction Reaction (ORR) and Oxygen Evolution Reaction (OER) applications. Graphene growth is carried out by the flow of methane and hydrogen gasses over various thickness cooper substrates cleaned by different methods (acetone and acetic acid). Characterization is performed with optical microscopy (SEM/EDS) and Raman/AFM spectroscopy. Results show noticeable differences in Raman signals and optical color contrast regarding the number and quality of layers of graphene and graphite, as well as distinctions between single-to-few- and multi-layer graphene, respectively. The graphene layers were delaminated using electrochemical procedure utilizing potentials below the threshold of hydrogen production, in order to avoid the formation of hydrogen bubbles resulting in the degradation of its conductivity. The electrochemical behavior of CVD growth graphene is studied by cycling voltammetry in acid and alkaline media on rotating disk electrode (RDE). The catalytic activity towards the OER was determined from Tafel plots obtained from galvanostatic current-voltage measurements.
Ultra-High Specific Power and Energy of Lithium-Ion Capacitors of the Composite Material between N-Doped Reduced Graphene Oxide (N-rGO) and Carbon Nanotubes (CNTs)
Authors: Aphirakaramwong Chalita , Phattharasupakun Nutthaphon , Sawangphruk Montree
Published: February 2020

By considering the advantages of lithium-ion batteries (LIBs) with remarkably high energy density and supercapacitors with high power density and long-life cycle, the emerging energy storage device has been introduced recently known as lithium-ion hybrid supercapacitors (LIHSs) or lithium-ion capacitors (LICs) providing the hybrid enhancement of those energy storage devices. However, to obtain the LICs with high power and energy density as well as long-life cycle, the combination of the electrochemical properties between LIBs and supercapacitors still have some difficulties hindering LICs’ applications such as instability of life cycles, and the appropriation of coupled materials electrodes which possibly suppress their particular properties of each materials rather than enhancing their features. Herein, the carbon-based composite materials consisting of N-doped reduced graphene oxide (N-rGO) and carbon nanotubes (CNTs) are inspirationally designed as promising candidate negative electrodes to challenge the electrochemical features of the LICs. The N-rGO/CNT composites are functionalized through the acid treatment by adding the functional groups on the network structures to investigate and obtain the remarkably combining benefit properties of high physical and chemical properties of both materials. This creates more defects, larger surface area and higher conductivity that could help to enhance the insertion and diffusion of the lithium ions. On the other hand, the activated carbon (AC) is selected as a positive electrode since it is a well-known electrode for supercapacitors due to its high surface area and appropriate pore sizes. The as-fabricated LIC exhibits the power density of 27748 W kg-1 and the energy density of 183 Wh kg-1 indicating their many potential applications as an ideal energy storage device.
Lithium-Ion Capacitors Based on Reduced Graphene Oxide/Carbon Nanotube Thin Films Fabricated By Electrostatic Spray Deposition
Authors: Adelowo Ebenezer , Rabiei Baboukani Amin , Wang Chunlei
Published: February 2020

Electrical double layer capacitors (EDLCs) are among important electrochemical energy storage devices for a wide variety of electronic systems, due to the fast charge and discharge capabilities, long cycle life and high power density they can provide. However, their low energy density remains a major drawback impeding their wide-spread applications. In order to overcome the low energy density limitation of EDLCs, lithium-ion based hybrid supercapacitors widely known as lithium-ion capacitor (LIC) have gained much attention. Lithium-ion capacitors basically combine the high energy density capability of lithium ion batteries and the high-power density of EDLCs. This is typically achieved by using a battery-type lithium intercalating anode material as the high energy density source, and a capacitor-type cathode as the high-power density source, in a lithium based organic electrolyte. Carbon in various forms is the most widely used and examined electrode material in electrochemical energy storage systems. Specifically, graphene, a two-dimensional (2D) carbon material is of great interest for electrochemical energy storage applications due to its attractive properties. In this work we employed lithiated reduced graphene oxide-carbon nanotubes (rGO-CNT) thin film as anode and pure rGO-CNT as cathode for lithium-ion capacitor. The thin films were prepared by electrostatic spray deposition (ESD). CNT was introduced to act as a spacer material to prevent the restacking of layered graphene and to enhance electrical conductivity of the graphene electrode material. Electrochemical performance of the LIC was evaluated by cyclic voltammetry, charge/discharge capacity, and electrochemical impedance spectroscopy (EIS). Material studies were also carried out on the electrode materials by scanning electron microscopy (SEM), X-Ray Diffractometry (XRD) and Fourier Transfer Infra-Red (FTIR). Detailed results obtained as well as the balancing strategy will be presented and discussed at the meeting.
(Invited) Multiscale Topological Design of Biological Interfaces to Novel Nanocarbons
Authors: Rastogi Sahil , Kalmykov Anna , Garg Raghav , San Roman Daniel , Cohen-Karni Tzahi
Published: February 2020

We focus on developing a new class of nanoscale materials and novel strategies for the investigation of biological entities at multiple length scales, from the molecular level to complex cellular networks. Our highly flexible bottom-up nanomaterials synthesis capabilities allow us to form unique hybrid-nanomaterials. Recently, we have demonstrated highly controlled synthesis of 3D out-of-plane single- to few-layer fuzzy graphene (3DFG) on a Si nanowire (SiNW) mesh template. By varying graphene growth conditions, we control the size, density, and electrical properties of the NW templated 3DFG (NT-3DFG). This flexible synthesis inspires formation of complex hybrid-nanomaterials with tailored optical and electrical properties to be used in future applications such as biosensing, and bioelectronics. Currently, we target the limits of cell-nanodevices interfaces using nanosensor based array assembled in 3D with subcellular spatial resolution (<5μm) and μsec temporal resolution. Our approach enables simultaneous multiplexed electrical measurements to directly monitor the development of electrical activities of microscale tissues (μtissues, ca. 100-400μm) which are engineered from induced pluripotent stem cell or embryonic stem cell derived cardiomyocytes. Last, we have developed a unique transparent graphene-based electrical platform that enables concurrent electrical and optical investigation of ES-derived cardiomyocytes’ intracellular processes and intercellular communication. In summary, the exceptional synthetic control and flexible assembly of nanomaterials provide powerful tools for fundamental studies and applications in life science, and open up the potential to seamlessly merge either nanomaterials-based platforms or unique nanosensor geometries and topologies with cells, fusing nonliving and living systems together.
Helical Polycarbodiimide-Cloaked Carbon Nanotubes for Biomedical Applications
Authors: Budhathoki-Uprety Januka , Korsen Joshua A. , Langenbacher Rachel E , Wayne Alysandria E. , Jena Prakrit Vaibhav , Heller Daniel A
Published: February 2020

Single-walled carbon nanotubes (SWCNTs) show promise in multiplexed bio-imaging and biosensing applications due to their photostable emission in the near infrared region, and the extreme optical sensitivity to the molecular environment. However, as produced, carbon nanotubes are insoluble and require surface functionalization prior to their uses in biomedical research. We non-covalently ‘cloaked’ carbon nanotubes with helical polycarbodiimide polymers to develop water soluble, biocompatible optical nanoprobes. The systematic modulation of the nanotube surface chemistry facilitates the development of new optical probes and sensors to study nano-bio interactions and allows the control of cellular delivery and sub-cellular localization of nanotubes in cancer cells.
Dual Color Bioimaging with Nanocarbon Quantum Dots
Authors: Hasan Md Tanvir , Gonzalez-Rodriguez Roberto , Sizemore Elizabeth , Naumov Anton V
Published: February 2020

Since a number of medical conditions require simultaneous treatment and diagnostics, the field of molecular therapeutics has recently turned to multifunctional approaches allowing for both therapy and biomedical imaging. A number of such molecular and nanoformulations are combined with fluorophores that allow for imaging of the delivery pathways of the drug in the visible. This is optimal for in-vitro or ex-vivo work, however, can not be utilized well in-vivo. Thus there is a need in nanoformulations optimized for both in-vitro and in-vivo studies. Nanocarbons, possessing intrinsic stable fluorescence in the visible and near-IR stand out as candidates for such complex application.

In this work, we for the first time produce a biocompatible nanocarbon quantum dots (NCQDs) that exhibit two-color emission both in visible and NIR possess a capability for biological pH sensing. These NCQDs show the crystalline graphitic structure in TEM and average sizes of c.a. 5 nm beneficial for cellular internalization. As opposed to related structures such as graphene oxide and other graphene derivatives NCQDs show high quantum yield in green (~500 nm) of 68.1% calculated via a comparative method using Coumarin-153 as a basis. Near-IR emission at ~860 nm shows lower relative quantum yield but is located in the water window with reduced absorption and lower autofluorescence backgrounds providing a promising potential route for in-vivo studies. Emission of NCQDs also depends on pH of the surrounding medium. The change in pH of as-prepared NCQDs from 2.71 to 8.2 yields an increase of fluorescence intensity up to ~60%. The actual spectral signature of NCQD emission also changes with pH: upon spectral decomposition of the broad emission feature the green component (470-514 nm) shows an increase at higher pH with respect to the red component (846-888 nm). Biocompatibility of NCQDs is verified by the MTT assay showing a low cytotoxic response. As potential drug delivery agents, NCQDs also show efficient cellular internalization assessed via in-vitro imaging in green. Additionally, pH-dependent shifts of the spectral features allow differentiating between acidic cancerous and neutral healthy exocellular environments allowing to use NCQDs for cancer detection. Therefore, our results indicate that NCQDs have a significant potential in bio-applications because of their capacity for dual color green/near-IR imaging for in-vitro/in-vivo studies, pH sensitivity, water solubility, low cytotoxicity and high capacity for cellular internalization.
(Invited) New Method Development for Making Structurally Defined DNA-Carbon Nanotube Hybrids
Authors: Zheng Ming
Published: February 2020

Many fundamental studies and technology development rely on structurally well-defined CNTs as well as corresponding coating layers. DNA-CNT library has been used successfully to select structurally well-defined hybrids. Existing selection methods have various drawbacks. In this talk, I will present our recent work in developing new aqueous two-phase separation systems for DNA-CNT selection as well as other computational approaches for efficient DNA library screening.
Nickel Nanoparticles Synthesized Via Novel Alcogel Electrolysis for the Growth of Multi-Walled Carbon Nanotubes (MWCNTs) By Chemical Vapor Deposition (CVD) Technique
Authors: Ali Zulfiqar
Published: February 2020

Facile Ni-silica nanocomposite synthesis method via alcogel electrolysis and their subsequent use for growth of multiwalled carbon nanotubes (MWCNTs) by conventional chemical vapor deposition (CVD) setup is reported. As the nature of nickel nanoparticles is magnetic so after synthesis amidst silica network these were magnetically separated. The catalysts were characterized by x-ray diffraction (XRD) and crystallite size was calculated from peak broadening of XRD data by using Sherr’s formula which was found to be 18-20 nm. Moreover, ethanol was employed as precursor of carbon along with Argon as inert carrier gas in CVD and three experiments on nickel nanocatalysts were performed in different temperature ranges i.e. 650 oC, 750 oC and 850 oC.

The grown multiwalled carbon nanotubes (MWCNTs) by CVD were characterized by XRD, Raman spectroscopy and Secondary Electron Microscopy (SEM). Raman spectroscopy confirms the high purity of grown MWCNTS on nickel nanocatalysts while from the SEM images the average diameter was found to be 25 nm and morphology of CNTs of grown carbon nanotubes on synthesized nickel nanoparticles were elucidated which shows nest type morphology characteristics of MWCNTs.

Key words: Alcogel Electrolysis, CVD, MWCNTS, Raman Spectroscopy.
Fullerene-Sensitized Carbon Nanotube Array Phototransistor with Responsivity Exceeding 107 A/W
Authors: Bergemann Kevin Joseph , Doty Frank Patrick , Léonard François
Published: February 2020

We present a carbon nanotube phototransistor using C60 as a sensitizer with responsivity exceeding 107 A/W (1010 V/W) under visible light. Carbon nanotube/C60 heterojunctions have previously been studied in photovoltaics. However, the responsivity of photovoltaics is limited by its lack of gain, with literature devices having responsivities less than 1 A/W. Our devices display significantly higher responsivity due to their phototransistor structure, with the C60 serving as the sensitizer to a carbon nanotube field-effect transistor. Excitons generated in the C60 diffuse to the heterointerface with the nanotube where they dissociate. Holes transfer to the nanotube and conduct away, leaving electrons bound on the nanotube surface which gate the transistor. The extreme sensitivity of the nanotube to local electric fields then results in a high responsivity. Devices are further improved by using an array of aligned nanotubes, which is significantly better in device current and responsivity compared to random network devices. The resulting devices are sensitive to less than 100 fW of incident light, offering a path forward to single photon detection.
(Invited) Degradable Conjugated Polymer with Exceptional Selectivity for Large Diameter Semiconducting Carbon Nanotubes
Authors: Gopalan Padma , Kanimozhi Catherine , Shea Matthew J , Brady Gerald J , Arnold Michael S.
Published: February 2020

Separation of electronically pure, narrow dispersed, pristine semiconducting single walled carbon nanotubes (S-CNT) from a heterogeneous as-synthesized mixture is essential for various semiconducting technologies and biomedical applications. While conjugated polymers are essential for this sorting step, it is highly desirable to remove any organic residues from the resulting devices. We report here the design and synthesis of a mild acid degradable π-conjugated polyimine polymer (PFO-N-BPy) that is structurally analogous to the commonly used and commercially available poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6’-(2,2’-bipyridine))] (PFO-BPy). An acid cleavable imine link (-HC=N-) was introduced in the PFO-N-BPy backbone to impart degradability, which is absent in PFO-BPy. PFO-N-BPy was synthesized via a metal catalyst free Aza-Wittig reaction in high yields. PFO-N-BPy with a degree of polymerization of just ~10 showed excellent (> 99% electronic purity) selectivity for both large diameter (1.3-1.7 nm) arc-discharge S-CNTs and smaller diameter (0.8-1.2 nm) HiPCO S-CNTs. Overall, selectivity for semiconducting species is similar to that of PFO-BPy but with an advantage of complete depolymerization under mild acidic conditions into recyclable monomers. We further show by UV-Vis, X-ray photoelectron spectroscopy (XPS), and SEM that the PFO-N-BPy wrapped S-CNTs can be aligned into a monolayer array on gate dielectrics using a floating evaporative self-assembly process from which the polymer can be completely removed. Short channel FETs were fabricated from the polymer-stripped aligned S-CNT arrays which further confirmed the semiconducting purity on the order of 99.9% or higher. We will present the recent optimized FET device results using this removable polymer.
(Invited) Functionalization of Carbon Nanotubes in a Micellar Environment
Authors: Orcin-Chaix Lucile , Delport Géraud , Campidelli Stephane , Voisin Christophe , Lauret Jean-Sébastien
Published: February 2020

A key issue for applications of colloidal nanoobjects is related to their solubility in water. Indeed, their aggregation results in the deterioration of their intrinsic properties. In order to solve this problem, many strategies have been developed. As far as carbon nanotubes are concerned, the best way to solubilize them in water while preserving their outstanding properties is to use a micellar environment. As a consequence the chemistry of carbon nanotubes in micelles is a growing field of research. For instance, people have grafted photoswitches on the wall of nanotubes, have doped nanotubes with diazonium and even performed polymerization in micelles [1-4].

In this presentation, we will present our recent results on the functionalization of carbon nanotubes with different kind of molecules in a micellar environment (porphyrins [5, 6], polymers [7]…). In particular, we will focus on the influence of the molecules on the optical properties of carbon nanotubes both on ensemble and at the single object level.

References

[1] AJ. Hilmer et al. Langmuir 28(2), 1309-1321 (2012)

[2]S. Kreft et al., J.Phys.Chem.C,119.27 (2015): 15731-15734

[3] G. Clavé, et al, Chem. of Mat. 25.13 (2013): 2700-2707

[4] Y. Tsutsumi RSC Advances 4, 6318 (2014)

[5] G. Delport et al, NanoLetters 17, 6778 (2017)

[6] G. Delport et al, Nanoscale 9, 2646-2651 (2017)

[7] L. Orcin-Chaix et al, submitted
Ionic Strength-Mediated Phase Transitions of Surface-Adsorbed DNA on Single-Walled Carbon Nanotubes
Authors: Salem Daniel , Gong Xun , Liu Albert Tianxiang , Koman Volodymyr , Dong Juyao , Strano Michael S
Published: February 2020

Single-stranded DNA oligonucleotides have unique, and in some cases sequence-specific molecular interactions with the surface of carbon nanotubes that remain the subject of fundamental study. In this work, we observe and analyze a generic, ionic strength-mediated phase transition exhibited by over 25 distinct oligonucleotides adsorbed to single-walled carbon nanotubes (SWCNTs) in colloidal suspension. The phase transition occurs as monovalent salts are used to modify the ionic strength from 500 mM to 1 mM, causing a reversible reduction in the fluorescence quantum yield by as much as 90%. The phase transition is only observable by fluorescence quenching within a window of pH and in the presence of dissolved O2, but occurs independently of this optical quenching. The negatively charged phosphate backbone increases (decreases) the DNA surface coverage on an areal basis at high (low) ionic strength, and is well described by a two-state equilibrium model. The resulting quantitative model is able to describe and link, for the first time, the observed changes in optical properties of DNA-wrapped SWCNTs with ionic strength, pH, adsorbed O2, and ascorbic acid. Cytosine nucleobases are shown to alter the adhesion of the DNA to SWCNTs through direct protonation from solution, decreasing the driving force for this phase transition. We show that the phase transition also changes the observed SWCNT corona phase, modulating the recognition of riboflavin. These results provide insight into the unique molecular interactions between DNA and the SWCNT surface, and have implications for molecular sensing, assembly, and nanoparticle separations.
(Invited) Quantification of DNA/SWCNT Solvation Differences By Aqueous Two Phase Separation
Authors: Jagota Anand , Yang Yoona , Shankar Akshaya , Aryaksama Thibault , Zheng Ming
Published: February 2020

Single wall carbon nanotubes (SWCNTs) coated with single-stranded DNA can be effectively separated into various chiralities using an aqueous two phase (ATP) system. Partitioning is driven by small differences in the dissolution characteristics of the hybrid between the two phases. Thus, in addition to being a separation technique, the ATP system potentially also offers a way to quantify and rank the dissolution properties of the solute (here the DNA/SWCNT hybrids), such as the solvation free energy or solubility. In this study, we propose two different approaches to analyze quantitatively the ATP partitioning of DNA/SWCNT hybrids. First, we present a model that extracts relative solvation free energy of various DNA/SWCNT hybrids by using an expansion relative to a standard state. Second, we extract a solubility parameter by analyzing the partitioning of hybrids in the ATP system. The two approaches are found to be consistent, providing some confidence in each as a method of quantifying differences in solubility of various DNA/SWCNT hybrids.
(Invited) Long-Lived Charge Separation across Interfaces with Semiconducting Single-Walled Carbon Nanotubes
Authors: Blackburn Jeffrey L. , Kang Hyun Suk , Ferguson Andrew John , Arias Dylan , Johnson Justin C.
Published: February 2020

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are attractive absorbers for use in solar energy harvesting schemes because of their strong and energetically tunable optical absorption, and high charge carrier mobilities due to the delocalized nature of the π-electron system. Beyond their technological potential, s-SWCNTs offer attractive properties for fundamental studies of charge generation in strongly confined nanoscale systems and photoinduced electron transfer (PET) processes. For example, strong quantum confinement and low dielectric screening impart single-walled carbon nanotubes with exciton-binding energies substantially exceeding kBT at room temperature. Additionally, the energetically narrow and distinct spectroscopic signatures for excitons and charges within s-SWCNT thin films enables the unambiguous temporal tracking of fundamental photophysical processes occuring at important photoactive heterojunctions designed for charge separation.

In this presentation, I will discuss recent studies that probe the generation and recombination of long-lived charges in samples consisting of heterojunctions between s-SWCNTs and various electron acceptors. I will focus on the roles of important interfacial properties that can influence the kinetics and efficiency of the interfacial PET process and recombination of the resulting separated charges. These properties include the energetic energetic driving force for exciton dissociation, the amount of residual wrapping polymer on the highly enriched s-SWCNTs, the local dielectric enrivonrment, the presence or absence of an electric field, and geometrical factors of the interface that can be modified via structural properties of the acceptors. Better fundamental understanding of these model interfaces can inform the design of more efficient solar energy harvesting systems, photodetectors, and other opto-electronic devices.
(Invited) Ultrafast Spectroscopy of Free-Carrier like Dynamics in Heavily Doped Semiconducting Carbon Nanotubes
Authors: Eckstein Klaus H , Achsnich Melanie M , Schoeppler Friedrich , Luer Larry , Hertel Tobias
Published: February 2020

We have investigated the photophysical properties of heavily doped semiconducting single-wall carbon nanotubes (s-SWNTs) in the vis and NIR spectral range. Doping is here achieved either by electrochemical gating or by redox chemistry, using AuCl3 as oxidizing agent. Stationary and time-resolved absorption spectroscopy show that the dynamical behaviour of electrochemically- and redox-doped s-SWNT samples are identical, indicating that doping mechanisms and the character of charged states is the same for both doping processes. Spectroscopically, the heavily doped regime is defined by the disappearance of NIR trion and neutral exciton signatures. The remaining absorption band in heavily hole-doped (6,5) s-SWNTs is broad, flat and practically featureless over a very broad spectral range from about 1150 nm to 620 nm. It carries nearly all the oscillator strength of the first subband exciton of intrinsic s-SWNTs. The transient spectral response of this so-called H-band (for heavily doped) is surprisingly weak, suggesting that signal contributions from ground- and excited state absorption and from stimulated emission cancel out nearly perfectly. We discuss these findings also in the context of UV-IR measurements of the optical conductivity which shows an ambiguous response in the low THz regime.
Facile Synthesis of Iron OXIDE/Carbon Shell for High Performance Lithium-ION Battery ANODE
Authors: Yan Yaping , Kang Yingbo , Park Ho Seok , Lee Hoo-jeong
Published: February 2020

Iron oxide, with a high theoretical capacity of ~1005 mAh/g, abundance, low cost and non-toxicity, has attracted special attention for energy storage applications. However, it still suffers from a long-cycle instability owing to its abnormal volume expansion during charge/discharge process. Herein, we explore possible ways to overcome the issue using iron oxide/carbon shell composites. A simple hydrothermal process is used to encapsulate iron oxide into carbon shell with the help of a template. The carbon shell has played two beneficial roles, one being the hard shell resisting the expansion of iron oxide and the other helping improve the electron transfer ability due its high conductivity. The morphology and crystal structure are characterized by ﬁeld emission scanning electron microscopy (FE-SEM) and XRD. The electrochemical performance of the as-prepared electrode material is investigated using CV and GCD measurements.
Multiple-Heterojunction in Single Titanium Dioxide Nanoparticle for Novel Metal-Free Photocatalysis
Authors: Cho Yoonjun , Kim Sungsoon , Park Jong Hyeok
Published: February 2020

Despite longstanding controversy, TiO2 polymorphs heterojunction composed of anatase and rutile outperform the individual ones because of the energetic type-II band alignment at the heterojunction interface. Apart from the conventional polymorphs interface, the surface disordered TiO2 has been drawing interest and considered as an unpredictable strategy while is regarded as a fact for dramatically enhancing photocatalytic activity. However, introduction and localization of the disordered layer within conventional TiO2 nanoparticles with the heterojunction has remained a big challenge.

Here we report a selective positioning of a disordered layer with different thickness ranges in between the anatase and rutile phases by a conceptually different synthetic route for highly efficient novel metal-free photocatalytic H2 production (denoted as DE-P25). With two step disorder engineering: Phase selective disordering of rutile TiO2 and thermal annealing process at temperature lower than phase transformation, the multiple heterojunction in DE-P25 single nanoparticle with the disordered layer of 2~3 nm could be synthesized which is confirmed by high resolution-TEM, electron energy loss spectroscopy (EELS) and inline electron holography mapping for the first time. EELS Ti-L2,3 spectrum geometry of DE-P25 showed distinctive oxygen-deficient variation between the two crystals which corresponds with the drastic decrease of potential and negative charge density within the disordered layer due to localized unpaired electrons. PL decay profiles exhibiting ultra-fast charge migration of DE-P25 indicate that the rutile phase incorporated with the disordered layer in the TiO2 nanoparticle induces dominant direct excition formation and reduces the self-trap of charge carriers, thus suppressing the electron/hole recombination, which perfectly coincides with the holography mapping analysis.

This multiple heterojunction in single TiO2 nanoparticles composed of crystalline anatase/disordered rutile/ordered rutile demonstrate not only superior interfacial charge separation efficiency, but also novel-metal free surface reactivity, which synergistically yields ~140 times higher H2 production rate than conventional anatase and rutile single heterojunction system.

Figure 1