Conductive Carbon Nanoparticles Research Articles

Integrating Mo2C/C as cocatalyst into S-scheme Mo2C/C/Co0.5Cd0.5S heterojunction with spatial photocarrier separation for photocatalytic synergistic H2 evolution

Reasonable design and production of potent photocatalysts for sustainable H2 production from solar energy is one of the necessary strategies in the photocatalysis process. The S-scheme heterojunction exposes remarkable superiority in boosting light harvesting and progressing photocarrier separation efficiency in the photocatalyst. Here, new S-scheme heterojunction Mo2C/C/Co0.5Cd0.5S photocatalysts, including different weights of noble metal-free Mo2C/C nanostructures as cocatalysts, were successfully synthesized. As expected, the nanocomposite structures exhibited increased photocatalytic activity relative to single Co0.5Cd0.5S. The nanocomposite containing 5 wt% Mo2C/C exhibited an increased hydrogen production efficiency of 83.86 mmol g−1 h−1, which was 8.4 times higher than single Co0.5Cd0.5S (10.06 mmol g−1 h−1). This implies that for Co0.5Cd0.5S, Mo2C/C increases visible light absorption, facilitates photocarrier separation, and boosts the H2 evolution rate. Moreover, conductive carbon nanoparticles, electron mediators with strong interfacial interaction, serve as rapid photocarrier transfer bridges between Co0.5Cd0.5S and Mo2C. In summary, the superb efficiency of Mo2C/C/Co0.5Cd0.5S is accredited to the synergistic effect between Co0.5Cd0.5S and Mo2C/C, the creation of S-scheme heterojunction, which assists the separation of photocarriers and declines the recombination possibilities. This research ensures a reference and new profound insight for understanding and designing noble metal-free cocatalyst-assisted S-scheme heterojunctions for immensely efficient photocatalytic H2 production.

Solid‐State Processing of Nascent Disentangled UHMWPE Reactor Powders Mixed with Carbon Nanoparticles

AbstractAspects of solid‐state processing of nascent disentangled ultra‐high‐molecular‐weight polyethylene (UHMWPE) powders of different syntheses mixed with electrically conductive carbon nanoparticles (NPs) of various types are studied. Effect of multiple parameters of the processing procedures on the electrophysical characteristics of the composite samples is investigated. Such parameters include time of preliminary ultrasonication (US) of NPs, time of US of UHMWPE/NPs mixtures, molding time, temperature, and pressure, deformation degree, etc. It is observed that by selecting optimal values of such parameters it is possible to obtain samples of composites with an extremely segregated structure made of the NPs, with NPs distributed evenly on the surfaces of the compacted UHMWPE powder particles. This ensures high levels of conductivity at very low values of NPs content. The segregated structure is retained when the composites are strengthened using the solid‐state uniaxial shear deformation process. While conductivity of most of the composites filled with various types of NPs monotonously decreases with the deformation ratio, conductivity of the composites filled with exceptionally long double‐walled carbon nanotubes is maintained. The processed oriented composites are also characterized by high EMR shielding properties, as well as interesting temperature dependencies of the electrical conductivity.

Construction and mechanism insights of a novel all-solid-state Z-scheme Mo2C/C/BiOI heterojunction for boosted photocatalytic degradation and reduction efficiency

Interfacial configuration of heterostructured photocatalysts to boost photocarrier separation and transfer is immensely beneficial to acquire great photocatalytic efficiency. Herein, a well-structured Mo2C/C/BiOI heterostructure containing different weight ratios Mo2C instead of noble metal was successfully prepared, where the inter-modified carbon nanosheets subserve as a connective to generate a perfect interface contact between Mo2C and BiOI. The photocatalytic performances of the photocatalysts were appraised by the degradation of indigo carmine and reduction of 4-nitroaniline under visible-light elucidation. The nanocomposite containing 7 % by weight of Mo2C/C showed the highest photocatalytic efficiency by eliminating 99.4 % of indigo carmine and 99.8 % of 4-nitroaniline within 75 min and 13 min, respectively. The boosted photocatalytic activity is attributed to the synergistic interaction between Mo2C/C and BiOI and the all-solid-state Z mechanism, where conductive carbon nanoparticles as an efficient electron mediator enable rapid photocarrier transfer and separation between Mo2C and BiOI. This study accentuates that Mo2C/C-based all-solid-state Z-scheme heterojunction nanocomposites are hopeful candidate photocatalysts for environmental applications.

Enabling stable and high-rate of an olivine-type cathode LiFePO4 for Li-ion batteries by using graphene nanoribbons as conductive agent

In this study, graphene nanoribbons (GNBs) were utilized as a conductive agent for the olivine structure-based cathode LiFePO4 to facilitate the fast redox reaction and enable a high-rate battery performance. As a result, the cathodes comprising 5 wt% graphene nanoribbons and 10 wt% conductive carbon nanoparticles exhibited the maximum capacity, 163.25 mAh.g−1 at 0.1C and 130.60 mAh.g−1 at 2C with excellent capacity retention after 100 cycles. In addition, graphene nanoribbons demonstrate positive impacts on the charge transfer process. Still, the high concentration of GNBs in the cathode weakens the adhesion properties and will need further optimization in the slurry mixing process.

Spark Desensitization of Nanothermites via the Addition of Highly Electro-Conductive Carbon Particles

In the past decade, the formulation of spark-desensitized nanothermites has considerably advanced, making them safe to handle. When ignited, these materials reveal impressive properties such as high temperatures (>1000 °C), intense heat releases (>kJ/cm3), and sometimes gas generation. Unfortunately, these energetic systems are systematically characterized by an extreme sensitivity to electrostatic discharges, which can cause accidental ignitions during preparation, handling, and transport. The present study examines the electrostatic discharge sensitivity response of an Al/WO3 energetic formulation doped with highly conductive carbon nanoparticles (Ketjenblack EC600JD). The results showed an increased threshold from <0.14 mJ to almost 40 mJ with 18.80 vol. % of KB EC600JD in the energetic mixture. The energetic material was also desensitized to friction stress with a threshold greater than 360 N, in contrast to a value of <4.9 N for an un-doped Al/WO3 energetic composite material. The reactive performance of the system (w/o Ketjenblack additive) was verified in open medium by means of an optical igniter. The heat release was determined by a calorimetric bomb and a decrease of 50% was recorded for the carbon-doped energetic system compared to the pristine Al/WO3 composition.

Highly sensitive and stable MEMS acetone sensors based on well-designed α-Fe2O3/C mesoporous nanorods

Highly sensitive and stable acetone gas sensors based on MEMS substrate supported carbon nanoparticles decorated mesoporous α-Fe2O3 (C-d-mFe2O3) nanorods (NRs) derived from Fe-MIL-88B-NH2 NRs were first synthesized via a sequential process including a facile hydrothermal reaction and one-step pyrolysis at a moderate temperature in air. The MEMS architecture ensures low power consumption, small size, and high integration of the sensor. The obtained C-d-mFe2O3 NRs exhibit good thermal stability and superior acetone sensing performance with excellent response (Ra/Rg = 5.2 to 2.5 ppm) and selectivity, fast response/recovery speed (10/27 s), and low detection limit of 500 ppb at 225 °C. Furthermore, the acetone sensor exhibits remarkable long-term stability and repeatability even after being stored in air for over 10 months. The enhanced acetone sensing performance could be attributed to the large specific surface area of mesoporous α-Fe2O3 NRs, highly conductive carbon nanoparticles on the surface, and the formation of α-Fe2O3/C heterojunction. Density functional theory (DFT) calculations help to further confirm the superior acetone sensing performance. The competitive performance makes C-d-mFe2O3 NRs gas sensor a great potential for practical application in environmental harmful acetone gas monitoring.

Porous Carbon/Borocarbonitride hybrid with enhanced tap density as a polar host for ultralong life Lithium-Sulfur batteries

The severe shuttle effect and sluggish redox kinetics are the current bottlenecks of lithium-sulfur (Li-S) batteries, resulting in capacity fading and inferior rate performance, especially under the condition of high sulfur loading and low electrolyte/sulfur ratio (E/S). Herein, conductive carbon nanoparticles (Ketjen Black, KB) covered by borocarbonitride (BCN) are assembled into micro-sized particles to form a polar KB@BCN hybrid, which is employed as a sulfur host with enhanced tap density via a facile intergrowth method. At a molecular level, BCN, endowed with abundant adsorption sites as the adsorbent and catalyst, can adsorb polysulfides and catalyze the conversion of polysulfides. On the nanometer scale, the BCN is loaded on the highly conductive KB nanoparticles, which can improve the conductivity of the hybrid (1786 S m−1), thereby improving the conversion of polysulfides. On the micrometer scale, the BCN and the KB nanoparticles together form micro-sized particles to improve the tap density, which is beneficial to build thick electrodes and reduce the amount of electrolyte. When applied as a sulfur cathode, KB@BCN-2 shows good cycling capability (a low-capacity decay of 0.05% after 800 cycles at 0.5C) and high rate performance (765 mA h g−1 at 3.0C). Even under a lean electrolyte condition (E/S = 5 μL mg−1), the KB@BCN-2-S has a high initial capacity of 1266 mA h g−1 at 0.1C. Significantly, incorporating polar electrocatalysts with carbon matrix to form a high-density sulfur host through secondary granulation can provide a new insight for achieving high-performance Li-S batteries.

Off/on switchable smart electromagnetic interference shielding aerogel

Summary Smart electromagnetic interference (EMI) shielding materials with tunable EM wave response characteristics are attractive for future EM devices. Here, we report an off/on switchable EMI shielding material that can be tuned from EM wave transmission to shielding and vice versa by mechanical compression and decompression. This smart material is prepared by filling conductive carbon nanoparticles into wood-derived lamellar carbon aerogel, showing reversible compressibility and strain-sensitive conductivity. The original aerogel has good impedance matching and low dielectric loss, allowing the EM wave to pass through. Mechanical compression enables the carbon nanoparticles to establish highly conductive pathways in the aerogel, which significantly increases the conductivity of aerogel and thus activates its EMI shielding performance. This function switch is reversible by repeatedly compressing and decompressing the aerogel. The availability of such a never-before-realized off/on switchable EMI shielding material provides an opportunity for the development of advanced smart EM devices.

Percolation Conduction of Carbon Nanocomposites.

Carbon nanocomposites present a new class of nanomaterials in which conducting carbon nanoparticles are a small additive to a non-conducting matrix. A typical example of such composites is a polymer matrix doped with carbon nanotubes (CNT). Due to a high aspect ratio of CNTs, inserting rather low quantity of nanotubes (on the level of 0.01%) results in the percolation transition, which causes the enhancement in the conductivity of the material by 10–12 orders of magnitude. Another type of nanocarbon composite is a film produced as a result of reduction of graphene oxide (GO). Such a film is consisted of GO fragments whose conductivity is determined by the degree of reduction. A distinctive peculiarity of both types of nanocomposites relates to the dependence of the conductivity of those materials on the applied voltage. Such a behavior is caused by a non-ideal contact between neighboring carbon nanoparticles incorporated into the composite. The resistance of such a contact depends sharply on the electrical field strength and therefore on the distance between neighboring nanoparticles. Experiments demonstrating non-linear, non-Ohmic behavior of both above-mentioned types of carbon nanocomposites are considered in the present article. There has been a model description presented of such a behavior based on the quasi-classical approach to the problem of electron tunneling through the barrier formed by the electric field. The calculation results correspond qualitatively to the available experimental data.

Percolation phenomena in nanocarbon composites

Nanocarbon composites present a new type of nanomaterials consisted of electric conducting carbon nanoparticles and a non-conducting matrix. A typical example of such composites is a polymer matrix doped with carbon nanotubes (CNT). Due to a high aspect ratio of nanotubes insertion of very small quantity of CNT (on the level of 0.01%) promotes the percolation transition resulting in an enhancement of the conductivity of the material by 10–12 orders of magnitude. Another type of nanocarbon composite is a film consisted of partially reduced graphene oxide (GO) produced as a result of thermal reduction of graphite oxide material. Distinctive peculiarity of both types of nanocomposites relates to the dependence of the specific resistivity of the materials on the applied voltage. Such a behavior is caused by non-ideal contacts between neighboring carbon particles involving into the composite. The resistance of this contact depends drastically on the intra-contact field, which promotes the dependence of the material resistivity on the applied voltage. The model description of such a non-linear dependence has been presented. The calculation results are compared with both literature data and the measured data obtained for reduced GO thermally treated at various temperatures.

Conductive carbon nanoparticles inhibit methanogens and stabilize hydrogen production in microbial electrolysis cells.

Nanosized conductive carbon materials have been reported to stimulate methanogenesis by anaerobic microbiomes, while other studies have shown their antimicrobial activities. The present study examined effects of conductive carbon nanoparticles (carbon black Vulcan, CB) on methanogenesis from glucose by anaerobic sludge. We found that a relatively high concentration (e.g., 2% w/v) of CB entirely inhibited the methanogenesis, where a substantial amount of acetate was accumulated after degradation of glucose. Quantitative real-time PCR assays and metabarcoding of 16S rRNA amplicons revealed that, while bacteria were stably present irrespective of the presence and absence of CB, archaea, in particular methanogens, were largely decreased in the presence of CB. Pure-culture experiments showed that methanogenic archaea were more seriously damaged by CB than fermentative bacteria. These results demonstrate that CB specifically inhibits methanogens in anaerobic sludge. We attempted to supplement cathode chambers of microbial electrolysis cells with CB for inhibiting methanogenesis from hydrogen, demonstrating that hydrogen is stably produced in the presence of CB.

Orientation of Anisotropic Carbon Particles in the Matrix of Reinforced Plastics by an AC Electric Field

In order to increase the shear strength of glass-fibers-reinforced plastics, a method has been developed for orientation of conductive carbon nanoparticles by an electric field applied transversely to the reinforcing fibers. Results of our research confirm the efficiency of the method offered — the shear strength the composites increased significantly, up to 35%, without reducing their other characteristics.

Investigation of polylactide and carbon nanocomposite filament for 3D printing

Fused deposition modeling (FDM) has been used to manufacture complicated structures and robots in the past few years. However, most FDM machines do not fabricate fully functional robots that are ready for use. One of the requirements of fully functional 3D printed robots is electrical connection in some part of the printed structure. Recently, electrically conductive commercial filaments are emerging to the market, but the actual chemical compositions of the filler and host materials as well as mechanical properties are not available. This paper presents composite materials consisting of conductive carbon nanoparticles, thermoplastics, and solvents to create thin filaments for 3D printing. The mechanical and electrical properties of the filaments fabricated using a composition of 0–15% weight of carbon nanoparticles (NC) in polylactide (PLA) and dichloromethane (DCM) solvent were investigated. The DCM is used for dissolving the PLA and dispersion of the NC, which is subsequently evaporated by drying. The electrical conductivity of the composite filament is compared with commercial and academia counterparts. Possible applications of the composite materials for fabrication of electrical circuitry for 3D printed robots were also discussed.

Changes in Proton and Electron Transfer Resistance in Cathode Catalyst Layer of PEM Fuel Cell By Carbon Corrosion

The structural robustness of the catalyst layer controlled by the morphology of the carbon support is closely related to the durability of the fuel cell. Electrochemical corrosion of the carbon support leads to the structural collapse of the cathode catalyst layer, decreasing the catalyst layer thickness. The collapse of the catalyst layer causes the increase in the oxygen diffusion resistance, which has been accepted as the major mechanism of the performance degradation of the fuel cell by carbon corrosion. However, little attention has been paid on the possibility of the damage of proton and electron pathway in the cathode catalyst layer by carbon corrosion and the resultant performance decay by the pathway damage. In this study, we introduce the fuel cell performance degradation mechanism in terms of the changes in proton and electron transfer resistance that is induced by the structural change of the cathode catalyst layer by carbon corrosion. Two types of cathode catalyst layer were prepared by adding electrically conductive carbon nanoparticles (Vulcan carbon) and electrically nonconductive silica nanoparticles into the typical Pt/C catalyst layer, respectively, as a model catalyst layer. The cathode catalyst layer consisted of a Pt/C (TEC10E50E) catalyst and long-side chain (Nafion IEC 1.00) ionomer binder. The electrolyte membrane was NRE211 (25 μm). Membrane electrode assemblies (MEAs) were fabricated by decal transfer process and their electrochemical characteristics were measured in a single cell. The accelerated stress test of the carbon corrosion was evaluated by applying a high potential of 1.4 V, and the change of the characteristics of the MEA was confirmed through electrochemical evaluation, before and after the carbon corrosion. The addition of nanoparticles to the cathode catalyst layer enhanced the structural stability of the catalyst layer regardless of the type of nanoparticles, which led to better durability in the catalyst layers added with nanoparticles after carbon corrosion. After carbon corrosion test, the cathode catalyst layer added with nanoparticles revealed a smaller decrease of catalyst layer thickness and a less increase of ohmic resistance than that of the catalyst layer without the nanoparticles. The different behavior of ohmic resistance change between the catalyst layers with and without the nanoparticles was closely related to the degree of damage in electron pathway in the cathode catalyst layer by carbon corrosion. The degree of proton resistance change in the catalyst layer was also dependent on the presence and the type of nanoparticles added to the catalyst layers.

Using Micro-Molding and Stamping to Fabricate Conductive Polydimethylsiloxane-Based Flexible High-Sensitivity Strain Gauges.

In this study, polydimethylsiloxane (PDMS) and conductive carbon nanoparticles were combined to fabricate a conductive elastomer PDMS (CPDMS). A high sensitive and flexible CPDMS strain sensor is fabricated by using stamping-process based micro patterning. Compared with conventional sensors, flexible strain sensors are more suitable for medical applications but are usually fabricated by photolithography, which suffers from a large number of steps and difficult mass production. Hence, we fabricated flexible strain sensors using a stamping-process with fewer processes than photolithography. The piezoresistive coefficient and sensitivity of the flexible strain sensor were improved by sensor pattern design and thickness change. Micro-patterning is used to fabricate various CPDMS microstructure patterns. The effect of gauge pattern was evaluated with ANSYS simulations. The piezoresistance of the strain gauges was measured and the gauge factor determined. Experimental results show that the piezoresistive coefficient of CPDMS is approximately linear. Gauge factor measurement results show that the gauge factor of a 140.0 μm thick strain gauge with five grids is the highest.

Conductive composites for oligonucleotide detection

A new method for oligonucleotide detection is presented based on oligonucleotide cross-linked polymer composites. Conductive carbon nanoparticles are incorporated into a DNA-functionalised polymer, containing partially complementary oligonucleotide cross-linkers, which is polymerised in situ upon interdigitated electrodes. In the presence of an aqueous solution of a specific analyte oligonucleotide sequence, the cross-linkers are cleaved, leading to increased swelling. As the polymer swells the relative density of the conductive particles decreases, leading to an easily measurable decrease in electrical conductivity. We demonstrate that such are capable of discriminating between analyte and control solutions, with single-base specificity, in under 3min. The lower detection limit of these composites is of the order of 10nM. The swelling characteristics of these composites is confirmed by optical imaging and the effects of varying temperature upon such composites are also reported.

Copper-Modified Covalent Triazine Frameworks As Efficient Electrocatalysts for Oxygen Reduction Reactions

1. Introduction Electrochemical oxygen reduction reaction (ORR) is important as a cathode reaction of various types of fuel cells. At present, platinum (Pt) is used as a practical ORR electrocatalyst. However, as Pt is scarce and expensive, development of electrocatalysts composed only of abundant elements is strongly required. One of the effective approaches to synthesize non-noble metal catalysts is to learn from enzymes. Cu ions in Cu-containing enzymes such as laccase serve as the active centers for ORR. Especially, multi-copper oxidases (MCOs) are representative enzymes that catalyze ORR with almost no activation energy [1]. For MCOs, the modulation of the electronic state of the copper (Cu) active sites through the coordination with amino acid residues is known to be essential for the superior ORR catalytic activity. Therefore, many studies have been conducted on developing Cu-complex based electrocatalysts that mimic the molecular structure of MCOs [2]. However, their catalytic activity and stability developed to date are not satisfactory. Covalent triazine framework (CTF) is a promising material as a novel platform for non-noble metal based electrocatalysts since the CTF is robust and possesses abundant nitrogen (N) atoms with electron lone pair for metal coordination. Recently, our laboratory has successfully synthesized Pt-modified CTF hybridized with conductive carbon nanoparticles (Pt-CTF) as methanol-tolerant ORR electrocatalyst [3]. However, modification of CTFs by non-noble metals has not been achieved yet. In this work, it was attempted to synthesize Cu modified CTF hybridized with carbon particles as an ORR electrocatalyst. 2.Experimental The CTF hybridized with conductive carbon particles was synthesized by in situ polymerization of 2,6-dicyanopyridine in the presence of carbon particles. Briefly, the mixture of ZnCl2 molten salt, 2,6-dicyanopyridine and carbon particles were placed in a vacuum-sealed pyrex glass tube and heated at 400 °C for 40 h. The modification of Cu atoms was performed by an impregnation method in CuCl2 solutions (Cu-CTF). Electrocatalytic activity was evaluated by conducting cyclic voltammetry (CV) in 0.1 M phosphate buffer solutions (PBS) at room temperature using a rotating ring disk electrode. The molecular structure of the catalyst was characterized by an extended X-ray absorption fine structure (EXAFS) and a transmission electron microscope (TEM). 3.Result and discussion The EXAFS and TEM results (not shown here) demonstrated that Cu atoms were coordinated to N atoms located in pores of the CTFs (Figure 1(a)). Figure 1(b) shows CVs for Cu-CTF and CTF in deaerated PBS (pH 7). The single pair of redox peaks corresponding to the Cu(I)/Cu(II) couple was observed for Cu-CTF. In the presence of dissolved oxygen, ORR current started to flow at the potential where Cu(II) is reduced to Cu(I) (Figure 1(c)), indicating that Cu(I) is the key species for the catalytic activity. Notably, both the redox potential of Cu(I)/Cu(II) (0.57 V) and the ORR onset potential (0.81 V) for the Cu-CTF were higher than those for the other Cu-complexes reported so far [4]. To clarify the molecular mechanism of ORR for Cu-CTF, we calculated the adsorption energy of O atom (ΔEo) as the indicator of interaction with ORR intermediates by the density functional theory (DFT) method. The result showed that Cu-CTF has similar ΔEo to platinum cluster which is the best artificial ORR catalyst. It strongly suggests that the regulation of the coordination structure by CTF modulates the interaction between reactant and metal centers [4][5]. Next, the stability of Cu-CTF during ORR was evaluated by conducting continuous CV cycles. For comparison, the Cu-(3,5-diamino-1,2,4-triazole) complex that shows similar ORR onset potential to the Cu-CTF [2] was also tested as a reference sample. For the conventional Cu-complex, the current density at 0.6 V decreased by 84 % after 500 cycles. However, the current decreased only by 19 % for the Cu-CTF, clearly indicating the superior stability of the Cu-CTF. 4.Conclusion Thus, it was demonstrated that newly-synthesized Cu-CTF could serve as an efficient ORR electrocatalyst in neutral solutions. Notably, the Cu-CTF exhibited the best activity and stability among the Cu-complex based electrocatalysts reported so far. 5.

Electrocatalytic Alcohol Oxidation By a Ruthenium-Modified Covalent Triazine Framework

Ruthenium (Ru) based catalysts, such as RuO2 and Ru complexes, have been widely studied for various oxidation reactions, such as oxygen evolution reaction (OER) and alcohol oxidation reactions (AOR). For example, RuO2 is an efficient anode catalyst for OER, which is a key reaction for artificial photosynthesis. However, as OER competes with AOR under the range of operating potentials, the high activity of RuO2 for OER results in the low Faradaic efficiency for AOR. In contrast, some Ru complexes are known to catalyze AOR with high efficiency [1]. However, as these Ru complexes are homogeneous catalysts, they are fragile and are difficult to separate and recycle. Recently, we have focused on covalent triazine frameworks (CTFs) as heterogeneous electrocatalysts. CTFs have 1,3,5-triazine units as linkers, and are representative microporous conjugated polymers. As CTFs possess abundant nitrogen (N) atoms with electron lone pair for metal coordination, CTFs are expected to stabilize Ru atoms through coordination with the N atoms like Ru complexes. Recently, we have indeed synthesized single-Pt atoms modified CTF hybridized with conductive carbon nanoparticles (Pt-CTF) as an electrocatalyst [2]. The Pt-CTF catalyzed the oxygen reduction with a high methanol tolerance, a unique property that was attributed to the atomic dispersion of Pt. In the present work, we successfully synthesized a Ru-modified CTF (Ru-CTF; Figure) and examined the electrochemical alcohol oxidation activity of this novel material. The Ru-CTF effectively oxidized alcohol with low OER activity. [1] TJ Meyer, M. Huynh, Inorganic chemistry, 2003, DOI 10.1021/ic020731v. [2] K. Kamiya, et al, Nat. Comm. 2014, 5, 5040. Figure 1

Conducting absorbent composite for parallel plate chemicapacitive microsensors with improved selectivity

Conducting absorbent composites were prepared using two organic polymers (polar and nonpolar) mixed with conductive carbon nanoparticles and an ionic liquid (BMIPF6). The mixture was deposited between the plates of chemicapacitive microsensors using ink-jet technology. Different coatings were characterized using SEM and DRIFTS techniques. The response magnitude for each sensor depends on numerous phenomenon but changes in permittivity of the analyte and polymer swelling dominate. The performance of individual chemicapacitive sensors were characterized through exposure to concentrations of various volatile organic compounds with different functional groups in a climate controlled vapor delivery system. Sensitivity, selectivity and limits of detection, of each prepared sensor, were compared and the discrimination power was evaluated using quadratic discriminant analysis. Ionic liquid doped polymers were able to enhance the sensitivity and the selectivity of parallel plate capacitive sensors. Improved analyte classification was achieved with the ionic liquid-doped polymers (97% accuracy) over the pure polymers. This preliminary study describes the first use of polymer composites with carbon black and ionic liquids as the absorbent dielectric layer in parallel plate microcapacitive sensors.

Platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles as methanol-tolerant oxygen reduction electrocatalysts.

Covalent triazine frameworks, which are crosslinked porous polymers with two-dimensional molecular structures, are promising materials for heterogeneous catalysts. However, the application of the frameworks as electrocatalysts has not been achieved to date because of their poor electrical conductivity. Here we report that platinum-modified covalent triazine frameworks hybridized with conductive carbon nanoparticles are successfully synthesized by introducing carbon nanoparticles during the polymerization process of covalent triazine frameworks. The resulting materials exhibit clear electrocatalytic activity for oxygen reduction reactions in acidic solutions. More interestingly, the platinum-modified covalent triazine frameworks show almost no activity for methanol oxidation, in contrast to commercial carbon-supported platinum. Thus, platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles exhibit selective activity for oxygen reduction reactions even in the presence of high concentrations of methanol, which indicates potential utility as a cathode catalyst in direct methanol fuel cells.