bluuebunny/crossref_metadata_2025 huggingface dataset:
The Structural Aspects of PFSA Ionomers As Determined By STEM and Simulations
Authors: Paddison Stephen J.
Published: February 2020

The need for next generation polymer electrolyte membrane fuel cells (PEMFCs) has driven considerable research effort into the development of novel membrane materials that are highly proton conducting at low temperatures. At present, perfluorosulfonic acid (PFSA) ionomers are the electrolyte of choice in current PEMFCs. PFSA ionomers including the benchmark Nafion™, consist of a hydrophobic poly-tetrafluoroethylene (PTFE) backbone with pendant perfluorinated vinyl ether side chains each terminated with a sulfonic acid group (i.e., –SO3H). The chemistry and molecular structure of the side chains and backbone in PFSAs play a crucial role in determining the hydrated morphology and transport properties especially in the presence of water. Under hydrated conditions, the mesoscale phase separation occurs due to the hydrophobic and hydrophilic segments of the macromolecules. This is mainly due to the aggregation of ionic clusters and the reorganization of the PTFE backbones, which have been investigated by a variety of experimental and modeling approaches.

We have recently examined the morphology of dry and hydrated perfluorosulfonic acid (PFSA) ionomers at cryo and room temperature using TEM/STEM with EELS capability. Z-contrast imaging was utilized to identify the micro-phase separation of the hydrophilic side chains containing water and the hydrophobic polytetrafluoroethylene (PTFE) backbones. The results compare very favorably with hydrated morphologies obtained through mesoscale dissipative particle dynamics (DPD) simulations. The cryo-STEM images of plunge-frozen samples was also found to agree with morphologies based on SAXS experiments. Chain conformations of the perfluorosulfonic acid (PFSA) ionomers: Nafion™ and Aquivion® were investigated with electron energy-loss spectroscopy (EELS) on a 200 kV transmission electron microscope (TEM) equipped with a monochromator. The results were compared with polytetrafluoroethylene (PTFE) to evaluate the effect of the pendant perfluoroether side chains of the ionomers on the structure of the PTFE backbone. Several unique spectroscopic features corresponding to conformational changes were identified in the low-loss region and the fine structures of the carbon K-edge. Results obtained from high-level density function theory (DFT) based electronic structure calculations confirm the conformational dependence of the EEL spectra of the PFSA ionomers. Comparison with the spectra obtained from the experiments revealed the correlation between the specific side chain chemistry and backbone conformation. This spectroscopic information will allow us to further explore the morphological properties of these materials when combining with additional imaging techniques.
High Transference Number Composite Lithium Electrolytes: From "Soggy Sand" Electrolytes to Infiltrated Mesoporous Silica
Authors: Popovic Jelena , Maier Joachim
Published: February 2020

High lithium transference number (tLi
+
) electrolytes are greatly beneficial as they could solve the problem of ion concentration gradients within the lithium cell which limit its lifetime and energy density. In composite “soggy sand” electrolytes (insulating oxide nanoparticles dispersed in lithium salt solution), lithium conductivity is enhanced in the space charge zones due to the coupled effects of anionic adsorption and association-dissociation equilibrium while the long range transport is enabled by beneficial particle network formation.1 When mesoporous silica particles are used as a solid phase, lithium can be efficiently transported through the interconnected pores (MSU-H, 7/15 nm).2 A convenient way of circumventing kinetical issues is infiltration of solid mesoporous silica pellets or monoliths (prepared by sol-gel method) with liquid electrolyte (1M lithium triflate in polyethylene glycol or dimethyl sulfoxide). Galvanostatic DC polarization measurements performed in a specially designed cell under controlled atmosphere indicate tLi
+
≈0.5 integrated with high AC conductivity (≈ 1 mS cm-1).3 The pertinence of such materials is remarkable as they could make lithium battery separators dispensable offering excellent contact/adhesion with high power nanostructured electrodes. Additionally, by careful choice of solvent, hybrid electrolytes can be made transparent which is beneficial for potential photoelectrochemical applications.

C. Pfaffenhuber, M. Göbel, J. Popovic, J. Maier, Phys. Chem. Chem. Phys., 2013, 15, 18318.

C. Pfaffenhuber, F. Hoffmann, M. Fröba, J. Popovic, J. Maier, J. Mat.
Chem. A, 2013, 1, 12560.

J. Popovic et. al., in preparation
Nanoparticle Imprinted Polymers As Sensing Layers for Size-Selective Recognition of Silver Nanoparticles
Authors: Witt Julia , Mandler Daniel , Wittstock Gunther
Published: February 2020

The expected broad utilisation of nanoparticles (NPs) calls for a detailed consideration of their specific toxicological effects and monitoring their release into the environment (nanotoxicology).[1] Appropriate in vitro sensing tools should provide information about the possible interaction between nanoobjects (characterized by core material, size, shell chemistry and shape) and biological systems. Recently, we published a new concept based on nanoparticle-imprinted polymers (NIPs, Figure 1) combined with electrochemical detection.[2] The new sensor principle was first demonstrated with a polyaniline film transferred simultaneously with template AuNPs by the Langmuir-Blodgett technique.

Here we demonstrate the extension of this concept to other matrix systems and other strategies for building NIPs. AuNPs with a diameter of 30 nm were arranged as templates on a 3-aminopropyltriethoxysilan (APTES)-modified indium tin oxide (ITO) electrode. Electrostatic interactions between negatively charged AuNPs and the positively charged monolayer enabled a controlled assembly of dispersed NPs as evidenced by scanning electron microscopy (SEM) and scanning force microscopy (SFM). Subsequently, a polymer matrix is generated either by electropolymerisation of self-inhibiting poly(phenol) and poly(plumbagin) films or by spin-coating an ultrathin poly(dimethylsiloxane) (PDMS) layer. SFM images proved the presence of templates within smooth, 5 to 20 nm thick matrices. Template NPs were chemically removed in potassium cyanide, leaving their shape and size imprinted in the polymer as evidenced by different techniques like SEM and Pulsed Force Microscopy (PFM). The recognition ability and size selectivity of NIPs was investigated by immersing the matrix in aqueous solutions containing citrate-capped AgNPs overnight. The presence of analyte AgNPs was verified electrochemically in an aqueous NaNO3 solution as by LSV. Complementing studies by UV-Vis and X-ray photoelectron spectroscopies corroborated the template embedding, template release and analyte NP uptake.

 References

[1] A. Nel, T. Xia, L. Mädler, N. Li, Science 311 (2006) 622.

[2] S. Kraus-Ophir, J. Witt, G. Wittstock, D. Mandler, Angew. Chem. Int. Ed. 53 (2014) 294.

Figure 1
Application of Polymer-Modified Electrode As Biosensor
Authors: Shaikh A. A. , Saha S. K. , Bakshi P. K. , Ahammad A. J. Saleh
Published: February 2020

A selective and highly sensitive electrochemical method was developed for the determination of potential biomolecules which contains hydroxyl functional groups. The electrochemical method, based on a poly(brilliant cresyl blue)-modified activated glassy carbon electrode was applied to determine hydroquinone (HQ) and catechol (CT) simultaneously. The modified electrode was characterized by cyclic voltammetry (CV) and scanning electron microscope (SEM). The modified electrode showed an excellent catalytic activity and enhanced reversibility toward the oxidation of both HQ and CT. The peak-to-peak separations (ΔEp) between oxidation and reduction waves in CV were decreased significantly from 360 and 285 mV at the bare electrode, to 59 and 56 mV at the poly(brilliant cresyl blue) modified electrode for HQ and CT respectively. Furthermore, the redox responses from the mixture of HQ and CT were easily resolved in both CV and differential pulse voltammetry (DPV). The oxidation peak currents of HQ and CT were linear up to 250 μM with the detection limits (S/N =3) of 60 and 56 nM for HQ and CT, respectively. The developed sensor was successfully examined for real sample analysis with tap water and it showed a stable and reliable recovery data with high reproducibility.
Glassy Carbon Electrode As a Promising Sensor for Healthcare and Environmental Monitoring
Authors: Chatterjee Sanghamitra , Chen Aicheng
Published: February 2020

Glassy carbon electrode (GCE) has been explored in the present investigations and applied thereafter for biomedical applications and environmental monitoring. A novel electrochemical approach for the quantitative analysis of methylglyoxal as a biomarker in human plasma has been developed. An electrochemical sensor employing a single walled carbon nanotube modified GCE for the sensitive detection of methylglyoxal is delineated for the first time employing square wave voltammetry. This modified electrode exhibits potent and sustained electron-mediating behavior and a well-defined reduction peak in response to methylglyoxal was observed. The interfering effect of common coexisting metabolites in human whole blood has also been investigated. The developed assay was shown to be specific and sensitive for the analysis of plasma levels of methylglyoxal in healthy volunteer and diabetic patients.

A simple, rapid and highly selective method for the determination of the most abundant α-dicarbonyl compound in wine and beer has been developed for the first time by employing square wave voltammetry. A novel electrochemical sensor, based on the electrodeposition of platinum nanoparticles onto single wall carbon nanotubes that were casted on a GCE substrate has been developed. This modified electrode was successfully applied for the quantitative analysis of methylglyoxal in wine and beer samples. The developed sensor possesses advantageous properties such as a high active surface area, stability, and a rapid electron transfer rate, which cumulatively demonstrate high performance toward the electrocatalytic reduction and detection of methylglyoxal.

A promising direct and simultaneous electrochemical determination method of phenolic pollutants in wastewater samples was constructed successfully on GCE with advantages being rapid, simple, convenient, sensitive, in situ and inexpensive. The electrochemical characteristics of multi-component phenolic pollutants, such as phenol and 4-nitrophenol were investigated on GCE employing square wave voltammetry technique. Each of them displayed good linear relationship between their oxidation peak currents and their corresponding concentrations in a rather wide range coexisting with the other phenolic pollutant. The effect of different experimental and instrumental parameters such as solution pH and square wave frequency were examined. Square wave voltammetry was employed to investigate the electrochemical characteristic of phenol and 4-nitrophenol at GCE and successfully realize the electrochemical separation and simultaneous determination of multi-component phenols at GCE without any modification for the first time.
Improving the the Actuation of Polymeric Artificial Muscles Using Magnetically Aligned Polyelectrolytes
Authors: Hasani-Sadrabadi Mohammad Mahdi , Jacob Karl I
Published: February 2020

Electroactive polymers comprise an emerging class of electromechanical actuators materials that can be used as biomimetic sensors and actuators in wide range of applications from medical devices to robotics applications. Among this class of smart materials, ionic polymer-metal composites (IPMCs) are considered most suitable for artificial muscles since they exhibit a large their large bending motion under relatively low input voltage, flexibility, biocompatibility, and lightweight properties. The polyelectrolytes membrane is a key part of the state-of-the art IPMC devices which act as an ion exchange media to support ionic transport and as a result bending motion of these structures. A recent morphological study of polyelectrolytes confirms the presence of hydrophilic ionic nanochannels that are randomly distributed laterally. These nanochannels are key players to tune the transport properties.

In the current research, we made Nafion/ Imidazole-functionalized superparamagnetic iron oxide nanoparticles (SPIONs) nanocomposite membranes and then by applying external magnetic field we made an induced alignment normal to the membrane’s surface. The effects of the anisotropic dispersion (alignment) of these nanoparticles on phase separation and ionic (H+, Li+, and Na+) conductivity of resulted membranes studied using small angle X-ray scattering (SAXS) and electrochemical impedance spectroscopy (EIS), respectively. Membranes with aligned nanodomains demonstrate higher bending forces as well as faster bending response (tip displacement rate). Due to formation of strong electrostatic interactions between sulfonated groups of Nafion and Imidazole groups at the SPION’s surface these structures display good performance in low humidity conditions as well. Results converge to indicate the effective presence of aligned nanoparticles especially in their functionalized state to tune performance of ionic polymer metal composite. This class of actuators can be applied for wide range of applications with different humidity conditions.
Preparation of PdCu Decorated Screen Printed Carbon Electrodes for Non-Enzymatic Hydrogen Peroxide Sensors
Authors: Uzunoglu Aytekin , Scherbarth Austin D , Stanciu Lia
Published: February 2020

In the last couple of years, Pd and its alloys gained considerable interest for non-enzymatic hydrogen peroxide (H2O2) and glucose sensing applications. Although Pd shows lower catalytic activity than Pt, its eco-friendly nature and low cost make it a promising catalyst material for many applications ranging from fuel cells to biosensors. Great effort has been devoted to improve the catalytic activity of Pd using various methods such as preparation of Pd nanostructures with different morphologies and alloy formation with transitional metals. In this work, Pd and PdCu alloys with varying compositions were deposited via a simple electrodeposition method on screen printed carbon electrodes (SPCEs) to fabricate non-enzymatic H2O2 sensors. Our results showed that co-deposition of Pd and Cu improved the electrochemical activity of the prepared electrodes significantly compared to pure Pd decorated SPCEs. The highest electrochemical activity was obtained from PdCu electrodes with (7:3) molar ratio. The sensitivity of this electrode to H2O2 was found to be -390.5 µA mM-1 cm-2 at the working potential of -300 mV (vs. Ag/AgCI). In addition, the electrodes showed a wide linear range of 0.5-6 mM and a low detection limit (0.3 µM).
Biosensors for Detecting Genetically Modified Organisms in Food and Feed
Authors: Chanysheva Alina , Arugula Mary , Vaglenov Kiril , Simonian Aleksandr
Published: February 2020

The detection of genetically modified organisms is of growing interest given their considerable presence in vast variety of food and feed ingredients, as well as their environmental impact. In this study we demonstrate real-time, label- free detection of DNA from genetically modified, Roundup Ready (RR) soybeans by surface plasmon resonance (SPR). Two single stranded (ss) DNA sequences were employed: 1) a thiol labeled (5'- SH) oligonucleotide allowing oriented covalent immobilization to the gold surface of the sensor which served as an anchor, and 2) probe sequence targeting the promoter of the (CaMV 35S) 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene present in RR soybeans. Our data indicate the limit of detection was as low as 2.0 nM. The system was also interrogated with target and non-target oligomeric mix and showed significant degree of specificity and selectivity. No binding was observed with non-target oligo injections. The sensitivity was as low as 8.0 nM when the target was in an excess mix of non-target sequences. This is the first step in developing a highly sensitive method for direct, label-free detection of genomic DNA from food products containing GMO soybeans.
(Nanocarbons Division Richard E. Smalley Research Award) Nanocarbons for Optoelectronic Applications
Authors: Guldi Dirk M.
Published: February 2020

Carbon is the key to many technological applications that have become indispensable in our daily life.  Altering the periodic binding motifs in networks of sp3-, sp2-, and sp-hybridized C-atoms is the conceptual starting point for a wide palette of carbon allotropes.  To this end, the past two decades have served as a test-bed for measuring the physico-chemical properties of low-dimensional carbon with the advent of fullerenes (0D), followed in chronological order by carbon nanotubes (1D), carbon nanohorns, and, most recently, by graphene (2D). These species are now poised for use in wide-ranging applications.

Expanding global needs for energy have led to a significant effort to develop alternatives to fossil fuels.  While alternative sources for energy are already in use, they comprise a small percentage of the energy demands needed to carry us through the 21st century.  No single source will solve the global needs, but the development of photovoltaics has vast potential as a point-of-use power source.  Recent work has shown that hybrid photoelectrochemical efforts with a percolation network of photon absorbers coupled to anelectron/hole transporter in combination with advanced photon management are the ideal design for realizing breakthroughs in high photon conversion efficiencies suitable for the catalysis of water.

I will report on our efforts regarding a unifying strategy to use the unprecedented charge transfer chemistry of 0D fullerenes, the ballistic conductance of 1D carbon nanotubes, the semiconducting features of carbon nanohorns, and the high mobility of charge carriers in 2D graphene, together in a groundbreaking approach to solving a far-reaching challenge, that is, the efficient use of the abundant light energy around us.

Leading References:

1) Malig, J. et al. " Toward Multifunctional Wet Chemically Functionalized Graphene – Integration of Oligomeric, Molecular, and Particulate Building Blocks that Reveal Photoactivity and Redox Activity", Acc. Chem. Res.
2013, 46, 53.

2) Guldi, D.M. et al. “Fullerenes For Organic Electronics”, Chem. Soc. Rev.
2009, 38, 1587.

3) Bottari, G. et al. “Covalent and Noncovalent Phthalocyanine-Carbon Nanostructure Systems: Synthesis, Photoinduced Electron Transfer, and Application to Molecular Photovoltaics”, Chem. Rev.
2010, 110, 6768.
(Invited) Graphene Molecules: Synthesis, Electronic Properties and Applications
Authors: Ji Zhiqiang , Doorn Stephen K. , Sykora Milan
Published: February 2020

Nanographene structures called Graphene Molecules (GMs) have been recently generating a growing interest. Theory predicts that these graphene fragments, comprising fewer than 300 carbon atoms (< 5 nm in size), are subject to quantum confinement effects similar to those observed in inorganic semiconductor quantum dots, but with different scaling laws, excited state properties and effects of functionalization. Predictions of unique size-dependent properties of GMs suggest the possibility that the studies of these structures may yield observation of interesting new phenomena and potentially development of new technologies. However, experimental studies of the electronic structure and demonstration of applications of GMs have so far been limited. This is in part due to challenges associated with the preparation of well-defined structures and in part due to the challenges in applying traditional methods in studies of GMs.

In the first part of my talk I will describe new method for a bottom up synthesis of well-defined GMs on metal oxide surfaces that we recently developed in our laboratory. The method, performed at ambient conditions, yields surface adsorbed GMs structurally and electronically equivalent to those synthesized in solution. The approach reduces the challenges associated with the tendency of GMs to aggregate and provides a convenient path for integration of GMs into optoelectronic applications. In the second part of my talk I will discuss results of our studies of charge transfer properties of GMs with optical band gaps tuned into visible wavelengths, facilitated by the new preparation method. I will show how an electrochemical potential can be used to inject one or more charges into GMs with a high level of control. I will show that the injection of charges leads to dramatic changes in GM absorption properties, quantitatively explain how the two are related and present insights into the kinetics of the charge injection. I will discuss how the basic understanding of the GM charging processes can be effectively exploited in a practical application, such as electrochromic device, wherein the graphene nanostructure is for the first time used as the optically active component. Finally, I will present the results of our studies of GMs as light harvesting components in sensitized solar cells (SSCs). In these studies we have found that mesoscopic TiO2/GM films can be used prepare stable SSCs with efficiencies of η ~1%. I will discuss the limitations and advantages of the GM-based SSC architectures.
(Invited) Tunable Thermoelectric Power Factor in Semiconducting Single-Walled Carbon Nanotube Networks
Authors: Ferguson Andrew , Avery Azure D. , Mistry Kevin S. , Guillot Sarah , Zhou Ben , Blackburn Jeffrey L. , Zink Barry L. , Kim Yong-Hyun
Published: February 2020

Single-walled carbon nanotubes (SWCNTs) are a versatile electronic material being explored as cost-effective, high-performance active materials in a variety of renewable energy applications such as transparent conducting or light-harvesting layers in photovoltaics and inclusions in thermoelectric composites.

We present a series of experiments focused on understanding the thermoelectric performance of enriched semiconducting SWCNT networks dispersed in a semiconducting polymer matrix. Rational choice of the semiconducting polymer allows us to sensitively tune the s-SWCNT diameter and band gap distributions within the composites. We use a stable charge-transfer dopant to control the density of carriers in the s-SWCNT network, as determined by the bleach of the absorption corresponding to the S11 excitonic transition. The performance of these transparent conducting s-SWCNT composite networks is comparable to neat p-type and n-type s-SWCNT networks doped by either nitric acid or hydrazine treatments. By varying the carrier density we are able to probe the relationship between the electrical conductivity and Seebeck coefficient (thermopower) in the s-SWCNT networks as a function of the carrier density and position of the Fermi energy. Although the electrical conductivity of the s-SWCNT networks is poor at very low carrier densities we have measured a colossal thermopower as high as ~2,500 µV/K, which is more than an order of magnitude larger than has been previously reported for SWCNT-based material systems and is consistent with theoretical calculations that consider the density of electronic states in individual s-SWCNTs. As we tune the carrier density, we are able to maintain a thermopower above 200 µV/K over almost the entire range of hole densities, corresponding to conductivities up to 1885 S/m, resulting in a thermoelectric power factor of ~100 µW/m·K2. These studies suggest that the low dimensionality of the SWCNTs has a stronger impact on the electrical conductivity than the thermopower, implying that they are less strongly coupled in these systems than is observed for compound inorganic semiconductors. These observations demonstrate the ability to exert exquisite control of the thermoelectric performance by tuning the carrier density and/or Fermi energy, and touts SWCNTs as an avenue for realizing thermally stable room temperature thermoelectric devices fashioned from inexpensive and abundant organic constituents.
(Invited) Single-Walled Carbon Nanotubes and Graphene As Highly Efficient Hole Collecting and Transport Layer for Solar Cells
Authors: Maruyama Shigeo , Cui Kehang , Chiba Takaaki , Jeon Il , Chen Xiao , Xiang Rong , Chiashi Shohei , Matsuo Yutaka
Published: February 2020

We investigate the application of single-walled carbon nanotubes (SWNTs) and graphene as hole extraction and transport layer in various kinds of solar cells including structured SWNTs-Si solar cell [1], dry-deposited SWNTs-Si solar cell [2], graphene-Si solar cells, organic solar cell [3] and perovskite solar cells. Using millimeter-scale monocrystalline single-layer graphene and honeycomb-structured SWNT network, the nanocarbon-Si solar cell demonstrated the air-stable power conversion efficiency (PCE) of 11.6% before any intentional doping process. For organic solar cells (OSC), the SWNT/MoOx/PEDOT:PSS nanocomposite was proposed and developed as hole extracting/electron blocking layer and electrode replacing ITO. Using PTB7/PC71BM mixture as active materials, the PCE of 6% was obtained for on glass substrate and 3.89% on flexible PET substrate. The hole collecting and transport function of SWNTs was also demonstrated in perovskite solar cells with high PCE. We expect that the carbon nanomaterials is very promising in the application solar cells.

References:

[1] K. Cui, T. Chiba, S. Omiya, T. Thurakitseree, P. Zhao, S. Fujii, H. Kataura, E. Einarsson, S. Chiashi, S. Maruyama, J. Phys. Chem. Lett., 4 (2013), 2571.

[2] K. Cui, A. S. Anisimov, T. Chiba, S. Fujii, H. Kataura, A. G. Nasibulin, S. Chiashi, E. I. Kauppinen, S. Maruyama, J. Mater. Chem. A, 2(2014) 11311.

[3] I. Jeon, K. Cui, T. Chiba, A. Anisimov, A. G. Nasibulin, E. I. Kauppinen, S. Maruyama, Y. Matsuo, to be submitted.
(Invited) CdTe Photovoltaic Devices Grown Directly on Transparent Carbon Single Wall Nanotube Back Contacts
Authors: Khanal Rajendra R. , Phillips Adam B. , Song Zhaoning , Xie Yao , Mahabaduge Hasitha P. , Heben Michael J.
Published: February 2020

CdTe/CdS solar cells were fabricated directly on 25 nm thick carbon single wall nanotube (SWNT) back contacts without the use of copper. Layers were deposited using a commercial, high temperature deposition process, and devices were finished with CdS layers grown by vapor assisted transport and chemical bath deposition.  The inclusion of the thin SWNT layer was absolutely essential for good device performance.  Device efficiencies were high despite the fact that the SWNT layer was supported on an n-type SnO2 layer that introduced a secondary n/p junction at the rear of the device. The champion device had an efficiency of 7.53%, which is close to the record value of 7.8% for a Cu-free substrate configuration device.[1] The use of a partially transparent back contact allowed comparison of device performance with front and backside illumination, which revealed several novel features of the SWNT back contact.

This work was supported by the U.S. Department of Energy under Award Number DE-SC0006349 and by faculty start-up funds from the University of Toledo.  We gratefully acknowledge samples and assistance from Mark D. Dorogi, Syed Zafar, and Gary T. Faykosh of Willard and Kelsey Solar Group.

(1)  I. Matulionis, S. Han, J. A. Drayton, K. J. Price, A. D. Compaan, MRS Online Proceedings Library 2001, 668, H8.23.
Energy Transfer Interactions Between Single-Chirality Swcnts and Photoactive Molecules
Authors: Xu Jia , Parra-Vasquez A. Nicholas G. , Subbaiyan Navaneetha K , Doorn Stephen K. , Montano Gabriel , Ziegler Kirk J , Duque Juan G.
Published: February 2020

Single-chirality single walled carbon nanotubes (SWCNTs) have unique optoelectronic properties that can be utilized in specific application, such as photovoltaics and biosensor. However, due to the large variety of SWCNTs and the difficulty of separation, the application of chiral SWCNTs are limited. Recently, a two-step aqueous two-phase extraction has been developed to allow a fast, high-yield separation of single-chirality SWCNTs. We aim to isolate different diameter SWCNTs and investigate photoactive molecule/SWCNT interactions such as porphyrins with different types of functional group. The structural influence of the porphyrin and their interaction with isolated SWCNTs of various diameters will be interpreted based on optical spectroscopic signatures of energy transfer. Further understanding will aid in the development of porphyrin-sensitized SWCNT photovoltaics thereby broadening the range of solar harvesting.
(Invited) Structured Carbon Nanostructures Derived from Graphene Oxide for Catalysis
Authors: Gupta Gautam
Published: February 2020

Carbon Nanostructures are at the heart of numerous energy conversion and storage applications including catalysis, fuel cells, super capacitors, and batteries. However, current technologies are marred with issues such as long-term durability under high potentials (e.g., fuel cells), low energy/power density (super capacitors), and metal intercalation issues (batteries). Research efforts worldwide have been focused on developing carbon nanostructures and especially graphene/graphene oxide materials with superior structural and functional properties for fuel cell applications. State-of-the-art devices have typically been synthesized from highly heterogeneous precursors and amorphous carbon materials. Catalysts derived from graphene and graphene-oxide (GO) are more homogeneous and possess properties, such as good chemical stability, excellent conductivity, and more importantly, can be functionalized in a controlled manner. These unique properties have led to explosion in research in areas of graphitic materials as catalyst support/material for ORR.

In this study, we report the synthesis of highly ordered carbon nanostructures derived from GO. Despite the widely known fact of the presence of residual water between the graphene oxide layers, only a few reports exist about the role of intercalated water.  We control the density of functional groups and inter-lamellar spacing of GO materials using low temperature drying treatments. The synthesized graphene oxide structures were subjected to reduction and nitrogen doping in different conditions to obtain an optimum oxygen reduction reaction catalyst. In this report, we focus on the affect of pre-treatment on the structure and function of the catalyst systems. We further demonstrate that the structure formed following the effective removal of intercalated water is crucial in the formation of active sites due to nano-confinement of water. Towards the end, we demonstrate a systematic shift in half wave potential and a significant decrease in peroxide production obtained depending upon the graphene oxide pretreatment.

Acknowledgment

Financial support from the Los Alamos National Laboratory Laboratory-Directed Research and Development (LDRD) Program is gratefully acknowledged.
Combinatorial Search of Hydrogen Catalysts Based on Transition Metal Embedded Graphitic Carbons
Authors: Choi Woon Ih , Wood Brandon , Schwegler Eric , Ogitsu Tadashi
Published: February 2020

To find right d-orbital configuration for hydrogen catalyst among embedded transition metal (TM) atoms into the lattice of graphene, we performed high-throughput computational search out of 300 combinatorial material pools. Theoretical criteria, so called descriptors regarding material stability and catalytic activity are considered and we were able to narrow down to ten materials for hydrogen evolution, two for hydrogen oxidation reaction. Since catalytically active sites are isolated to single TM atom, Volmer-Kubas type of new reaction pathway is expected for hydrogen evolution. Earth-abundant element Mo, bulk form of which doesn’t show good catalytic activity at all, turns into catalytically active site as it is dispersed atomically and its d-orbitals splits by the symmetry of local coordination at the binding sites.
Gold Decorated Graphene for Energy Conversion in Electrocatalytic Oxidaton of Alcohols
Authors: Ventrapragada Lakshman K , Podilla Ramakrishna , Rao Apparao M , Creager Stephen
Published: February 2020

Graphene due to its high surface area and superior conductivity has attracted wide attention from both industrial and scientific communities. We chose graphene as a substrate for metal nanoparticle deposition with possible fuel cell applications. There are many chemical routes for fabrication of metal-graphene composites, but they have an inherent disadvantage of low performance due to the usage of surfactants, that adsorb on their surface. Here we present a design for one pot synthesis of gold nanoparticles and simultaneous deposition on graphene with laser ablation of gold strip and functionalized graphene. In this process there are two natural advantages, the nanoparticles are synthesized without any surfactants, therefore they are pristine and subsequent impregnation on graphene is linker free. These materials are well characterized with electron microscopy to find their morphology and spectroscopic techniques like Raman, UV-Vis. for functionality. This gold nanoparticle decorated graphene composite has been tested for its electrocatalytic oxidation of alcohols for alkaline fuel cell applications. An electrode made of this composite showed good stability for more than 200 cycles of operation and reported a low onset potential of 100 mV more negative, an important factor for direct extracting energy from ethanol.

Figure 1
(Keynote) Paper-Based Lateral Flow Strips Toward Point-of-Care Detection of Biomolecules
Authors: Wu Nick , Zheng Peng , Gao Xuefei
Published: February 2020

This talk shows our effort to develop the paper-based lateral flow strips as point-of-care devices. The detection platforms based on different signal transduction mechanisms have been developed. The detection platforms have then been integrated into the paper-based membrane to form the lateral flow strips.  The paper-based lateral flow strips are inexpensive, require only a hundred of micro-liter sample and minimize the sample pre-treatment in the lab setting.
A Fully Inkjet-Printed Carbon Nanotube Electrochemical Sensor on Paper
Authors: da Costa Tallis H. , Tortorich Ryan P. , Song Edward , Choi Jin-Woo
Published: February 2020

We present a fully inkjet-printed electrochemical sensor on paper, which uses inkjet-printed carbon nanotubes as the working, counter, and reference electrodes. Although paper-based electrochemical sensors have been demonstrated previously, our method of fabrication is both faster and cheaper and fully inkjet-printed. Due to its superior patterning ability, inkjet printing allows for the fabrication of on-demand paper-based electrochemical sensors without the use of templates or post-deposition photolithography. Additionally, in combining inkjet printing with an exciting material like carbon nanotubes rather than common metals (i.e. gold and silver), the fabrication cost is further reduced, and the possibility for mechanically flexible sensors becomes a reality.

The use of paper as a substrate offers many advantages over other possible rigid substrates as well as flexible polymer substrates. Of course, paper is indeed a renewable resource and thus is a very cost-effective substrate for fabrication of disposable sensors. Additionally, paper is naturally flexible, preventing damage to the sensor upon external stress during use. Finally, paper is a great candidate for microfluidic applications due to its superb ability to transport liquids.

The fabrication process is remarkably simple. The electrode design was developed using any drawing software or CAD.  Multi-walled carbon nanotubes (MWCNTs) were dispersed in deionized (DI) water using sodium dodecyl sulfate (SDS), an anionic surfactant.  More specifically, a bottle containing 10 mg/ml of MWCNTs and 8 mg/ml of SDS was sonicated for 30 minutes and centrifuged at 12,000 rpm for 5 minutes. The carbon nanotube ink was then injected into a clean ink cartridge and printed using an office inkjet printer.

In order to ensure proper functionality, a low electrode resistance was necessary. This was achieved by printing the carbon nanotube ink multiple times to reduce the sheet resistance. We were able to achieve less than 2 k-ohm/square with 20 prints on paper. The sensor was tested with various concentrations of FeSO4 in 0.1 M H2SO4. A simple potentiostat circuit was used along with a LabView FieldPoint module for voltage control and current measurement. Potential step voltammetry was employed and the saturation current was used as a means to determine analyte concentration.
Multimode Microsensors Based on Carbon Matrices for the Screening of Whole Blood for IL-6
Authors: Stefan-van Staden Raluca-Ioana , Gugoasa Livia A
Published: February 2020

High levels of interleukin-6 are associated with prostate cancer, breast cancer, stress, lupus, cardiovascular diseases and obesity. A fast and simple method of screening for IL-6 is needed for early diagnosis of these conditions. Therefore, multimode sensors based on cabon matrices, such as graphite, graphene, fullerene C60, and multiwall carbon nanotubes modified with maltodextrin were designed for the assay of IL-6 in whole blood samples. The best limit of determination (10fg/mL) was recorded when the microsensor based on maltodextrin immobilized in C60 fullerenes was used for the assay of IL-6 in whole blood samples.

Acknowledgements The present work was supported by UEFISCDI, Romania PNII, Ideas (2011-2015), Contract-no. 123/2011.
(Keynote) Near-Zero-Power Electrochemical Sensors for Wearable Wireless Health, Safety, Surveillance and Environmental Electronics
Authors: Stetter Joseph R , Carter Michael T , Stetter Edward F
Published: February 2020

An emerging GDP revolution based on fusion of computing, communication, and sensing will bring a state of “abundance” and create the largest bull market in history [1]. Technical global tides including the Internet of Things (IoT), Mobile/Wearable electronics, Digital Health, and context computing are driving the need for billions of sensors.  Healthcare will require 50 or more sensors on the body and will shift emphasis in healthcare from diagnosis of disease to the business of wellness.  Amazon has introduced a wearable electronics section validating this new market segment and acknowledging the rapid growth. The IoT with cloud and fog computing is planning to use trillions of sensors for “crowd” monitoring of our health, safety, security, and environment.  The disruptive characteristic of the needed gas sensors always includes low power but the technology must also be low cost and scalable to high volumes in order to be successful in high volume applications.  These restrictions also usually come with the need for high performance and small unobtrusive packaging.

Herein we report the smallest amperometric sensor we have made to date [5x5x1mm, below] and their performance. The amperometric sensor technology actually generates a small current [few nA] and, in some cases, can be galvanic and require no external power to operate. The sensors typically utilize a low power potentiostat [1.2 nA at 3 V] as well as sense the gases around and inside of us performing breath and environmental analysis. The gas sensors are combined with low-power or energy harvesting circuits for computing, reporting, and communication to provide situational awareness on mobile platforms and in our infrastructure.  The new sensors are made using PE [printed electronics] technology that can be scaled to billions of units and are sensitive to breath gases [e.g., acetone, alcohol, CO] and environmental gases [CO, NO2, SO2, ozone] at ppb and ppm levels with rapid response, multi-year lifetime and often important selectivity. Consumer products are in the stores starting in the fall of 2014 using the newest SPEC sensors [2] and the technology is reported here.  

1] T-Sensors Summit, November 11-13, 2014, San Diego, CA,  www.Tsensors.org.

2] www.spec-sensors.com.

Figure 1
A Novel Viscometer Based on Self-Propelled Nanomotor
Authors: Li Longqiu , Li Tianlong , Wang Jiyuan , Zhang Guangyu
Published: February 2020

Liquid viscosity is a vital metric in the field of mciroelectromechanical systems (MEMS), and nanoelectromechanical systems (NEMS). However, the complexity and high cost of the measurement in micro scale are prompting unconventional route for detecting viscosities. Since the velocity of nanomotor is mainly determined by the viscosities of solution, the nanomotor can potentially be used to measure the viscosity of solution. In this work, a self-propelled nanomotor based viscometer is developed, and studied both theoretically and experimentally. A hydrodynamic model to describe the motion of nanomotor is proposed to investigate the relationship between the viscosity and the velocity of nanomotor. The effect of the material properties and geometric parameters of nanomotor on the accuracy of viscometer are identified experimentally. In addition, a comparison between the numerical and experimental results is also provided.
(Keynote) Oxygen Sensing Microfluidic Structures for Biomedical and Environmental Science Research
Authors: Grate Jay W , Kelly Ryan , Anheier Norm , Suter Jonathan , Schmidt Tom , Vasdekis Andreas
Published: February 2020

Planar optode films consisting of a fluorescent dye in a polymer film can be incorporated into microfluidic structures to map out oxygen concentrations while microfluidic devices set up gradients and environmental conditions that are relevant to biomedical or natural biogeochemical systems.  Gradients of molecular oxygen are of particular interest due to the fact that many important biological processes either occur at interfaces or are regulated by the flux of oxygen and other resources.  Hence, oxygen sensing microfluidic devices can be used to investigate microbial behavior related to carbon cycling, or microbial communities in the gut where the interface with the host tissue is microoxic.  In addition, oxygen sensing microfluidic devices may be useful in mammalian cell or tissue culture where favorable conditions must be maintained.  Practical issues in developing and fabricating microfluidic structures with inherent oxygen sensing capability include multiple parameters, including incorporation of sensing elements in microfluidics, imaging oxygen concentrations by fluorescence, and relating oxygen imaging data to spatial structure of the microfluidic channels, all in useful structures that create biologically relevant microenvironments.  We will describe multiple approaches to meeting these challenges, including gas impermeable silicon-on-glass structures where the fluorescent signals are only observed where microfluidic channels occur, and solvent imprinting lithography where sensing dyes can be incorporated in thermoplastics in a single process that enables sensor dye impregnation, channel imprinting, and cover plate bonding.  These methods are discussed with regard to structures including pore network and gradient generation microfluidic structures.
Estimation of Crystalline Structure and Gas Transport Properties of Crystalline Fluorinated Copolymer
Authors: Matsuba Go , Nyuui Tatsuki , Sato Shuichi , Nagai Kazukiyo
Published: February 2020

PFA has a unique role in the plastics industry due to its inertness, heat resistance, and low coefficient of friction in a wide temperature range.  Generally speaking, fluorinated compounds and fluoropolymers have excellent chemical resistance, and oil- and water-shedding resistance. They have been used as rubbers at high temperatures and in several lubricating fluorine manufactured products.

Anyway, the crystalline polymers were used in the gas permselective, barrier and separating films. The gas transport properties are related to solubility, diffusivity and permeability in a polymer. In general, gas permeability, diffusivity, and solubility decrease with increasing crystallinity in a polymer film, because of gas molecules cannot diffuse and dissolve in the crystalline region. A few paper reported gas transport properties of PFA. In these papers discussed film thickness, pressure and grade dependence of gas permeability in PFA. However, there has been no systematic research on the relationship between gas transport properties and crystalline structure in PFA.

We have investigated the relationship between amorphous structure and its gas permeability of Poly(tetrafluoroethylene-co-perfluoroethylvinylether) (PFA) films using differential scanning calorimetry (DSC), wide-angle, small-angle X-ray scattering and quasi-elastic neutron scattering measurements. We focused on the hierarchical inter-lamellar amorphous structure of various gas-permeable PLA films.  For controling cooling rate from the molten state, we prepared various crystallinity sample.  The crystallnity range is between 29.3% (melt quenched) and 38.3 % (cooling rate, 0.5 K/min). 

From wide-angle x-ray scattering measurements, the crystal lattice is independent of cooling rate, however, the lamellar crystal structure is strongly dependence on the cooling rate.  The thickness of lamellar crystal and amorphous increase with decreasing cooling rate.  The gas permeability coefficient was almost independent of crystallinity, that is, below crystallinity of 32 %, the gas permeability and diffusivity decreases with increasing crystallinity, while above that of 32%, it is independent of crystallinity.  The order of gas permeability coefficient of all PFA films was the same as that of gas size such as the kinetic diameter: 2.89 Å (H2), 3.30 Å (CO2), 3.46 Å (O2), 3.64 Å (N2), 3.80 Å (CH4).   The gas molecules might pass through the amorphous region of inter-lamellar crystals.  Furthermore, we evaluated the relaxation processes of various crystallnity PFA films with quasi-elastic neutron scattering measurements.  The films has two relaxation mode, 10^-12 s and 10^-13 s.  The longer relaxation time component (~10^-12 s), which was assigned as "relaxation of side chain", has correlated with gas permeability.