Three-dimensional porous reduced graphene oxide/PEDOT:PSS aerogel: Facile preparation and high performance for supercapacitor electrodes

Comparison of the analytical performance of two different electrochemical sensors based on a composite of gold nanorods with carbon nanomaterials and PEDOT:PSS for the sensitive detection of nitrite in processed meat products

Herein, two platforms for electrochemical sensors were developed based on a combination of gold nanorods (AuNRs) with electrochemically reduced graphene oxide (ErGO) or with multiwalled carbon nanotubes (MWCNTs) and PEDOT:PSS for nitrite detection. The first and second electrodes were denoted as AuNRs/ErGO/PEDOT:PSS/GCE and AuNRs/MWCNT/PEDOT:PSS/GCE, respectively. Both materials for electrode modifiers were then characterized using UV-Vis and Raman spectroscopy, SEM, and HR-TEM. In addition, both sensors exhibit good electrochemical and electroanalytical performance for nitrite detection when investigated using voltammetric techniques. The synergistic effect between the AuNRs and their composites enhanced the electrocatalytic activity toward nitrite oxidation compared with the unmodified electrode, and the electroanalytical performance of the second electrode was superior to the first electrode. This is because the high surface area and conductivity of the MWCNTs in the second electrode provide the highest electrochemically active area (0.1510 cm2) among the other electrodes. Moreover, the second electrode exhibited a higher value for the surface coverage and the diffusion coefficient than the first electrode for nitrite detection. The electroanalytical performances of the first and second electrode for nitrite detection in terms of concentration range are 0.8-100 μM and 0.2-100 μM, limit of detection (0.2 μM and 0.08 μM), and measurement sensitivity (0.0451 μA μM-1 cm-2 and 0.0634 μA μM-1 cm-2). Good selectivity was also shown from both sensors in the presence of NaCl, Na2SO4, Na3PO4, MgSO4, NaHCO3, NaNO3, glucose, and ascorbic acid as interfering species for nitrite detection. Furthermore, both sensors were employed to detect nitrite as a food preservative in the beef sample, and the results showed no significant difference compared with the spectrophotometric technique. These results indicate that both proposed nitrite sensors may be further applied as promising electrochemical sensing platforms for in situ nitrite detection.

A Review of Graphene-Based Materials/Polymer Composite Aerogels

The fabrication of composite materials is an effective way to improve the performance of a single material and expand its application range. In recent years, graphene-based materials/polymer composite aerogels have become a hot research field for preparing high-performance composites due to their special synergistic effects in mechanical and functional properties. In this paper, the preparation methods, structures, interactions, properties, and applications of graphene-based materials/polymer composite aerogels are discussed, and their development trend is projected. This paper aims to arouse extensive research interests in multidisciplinary fields and provide guidance for the rational design of advanced aerogel materials, which could then encourage efforts to use these new kinds of advanced materials in basic research and commercial applications.

Pedot:PSS/Graphene Oxide (GO) Ternary Nanocomposites for Electrochemical Applications

Among conductive polymers, poly(3,4 ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has been widely used as an electrode material for supercapacitors, solar cells, sensors, etc. Although PEDOT:PSS-based thin films have acceptable properties such as good capacitive and electrical behaviour and biocompatibility, there are still several challenges to be overcome in their use as an electrode material for supercapacitors. For this reason, the aim of this work is to fabricate and characterise ternary nanocomposites based on PEDOT:PSS and graphene oxide (GO), blended with green additives (glucose (G) or ascorbic acid (AA)), which have the benefits of being environmentally friendly, economical, and easy to use. The GO reduction process was first accurately investigated and demonstrated by UV-Vis and XRD measurements. Three-component inks have been developed, and their morphological, rheological, and surface tension properties were evaluated, showing their printability by means of Aerosol Jet® Printing (AJ®P), an innovative direct writing technique belonging to the Additive Manufacturing (AM) for printed electronics applications. Thin films of the ternary nanocomposites were produced by drop casting and spin coating techniques, and their capacitive behaviour and chemical structures were evaluated through Cyclic Voltammetry (CV) tests and FT-IR analyses. CV tests show an increment in the specific capacitance of AAGO-PEDOT up to 31.4 F/g and excellent overtime stability compared with pristine PEDOT:PSS, suggesting that this ink can be used to fabricate supercapacitors in printed (bio)-electronics. The inks were finally printed by AJ®P as thin films (10 layers, 8 × 8 mm) and chemically analysed by FT-IR, demonstrating that all components of the formulation were successfully aerosolised and deposited on the substrate.

Vertically Ordered Mesoporous Silica-Nanochannel Film-Equipped Three-Dimensional Macroporous Graphene as Sensitive Electrochemiluminescence Platform

Three-dimensional (3D) electrochemiluminescence (ECL) platform with high sensitivity and good anti-fouling is highly desirable for direct and sensitive analysis of complex samples. Herein, a novel ECL-sensing platform is demonstrated based on the equipment of vertically ordered mesoporous silica-nanochannel films (VMSF) on monolithic and macroporous 3D graphene (3DG). Through electrografting of 3-aminopropyltriethoxysilane (APTES) onto 3DG as molecular glue, VMSF grown by electrochemically assisted self-assembly (EASA) method fully covers 3DG surface and displays high stability. The developed VMSF/APTES/3DG sensor exhibits highly sensitized ECL response of tris(2,2'-bipyridyl) ruthenium (Ru (bpy)3 2+) taking advantages of the unique characteristics of 3DG (high active area and conductivity) and VMSF nanochannels (strong electrostatic enrichment). The VMSF/APTES/3DG sensor is applied to sensitively detect an important environmental pollutant (4-chlorophenol, with limit of detection or LOD of 30.3 nM) in term of its quenching effect (ECL signal-off mode) toward ECL of Ru (bpy)3 2+/tri-n-propylamine (TPrA). The VMSF/APTES/3DG sensor can also sensitively detect the most effective antihistamines chlorpheniramine (with LOD of 430 nM) using ECL signal-on mode because it acts as co-reactant to promote the ECL of Ru (bpy)3 2+. Combined with the excellent antifouling ability of VMSF, the sensor can also realize the analysis of actual environmental (lake water) and pharmaceutical (pharmacy tablet) samples. The proposed 3D ECL sensor may open new avenues to develop highly sensitive ECL-sensing platform.

Structural Engineering of Hierarchical Aerogels Comprised of Multi-dimensional Gradient Carbon Nanoarchitectures for Highly Efficient Microwave Absorption

Recently, multilevel structural carbon aerogels are deemed as attractive candidates for microwave absorbing materials. Nevertheless, excessive stack and agglomeration for low-dimension carbon nanomaterials inducing impedance mismatch are significant challenges. Herein, the delicate "3D helix-2D sheet-1D fiber-0D dot" hierarchical aerogels have been successfully synthesized, for the first time, by sequential processes of hydrothermal self-assembly and in-situ chemical vapor deposition method. Particularly, the graphene sheets are uniformly intercalated by 3D helical carbon nanocoils, which give a feasible solution to the mentioned problem and endows the as-obtained aerogel with abundant porous structures and better dielectric properties. Moreover, by adjusting the content of 0D core-shell structured particles and the parameters for growth of the 1D carbon nanofibers, tunable electromagnetic properties and excellent impedance matching are achieved, which plays a vital role in the microwave absorption performance. As expected, the optimized aerogels harvest excellent performance, including broad effective bandwidth and strong reflection loss at low filling ratio and thin thickness. This work gives valuable guidance and inspiration for the design of hierarchical materials comprised of dimensional gradient structures, which holds great application potential for electromagnetic wave attenuation.

A high-performance asymmetric supercapacitor-based (CuCo)Se2/GA cathode and FeSe2/GA anode with enhanced kinetics matching

The performance of asymmetric supercapacitors (ASCs) is limited by the poorly matched electrochemical kinetics of available electrode materials, which generally results in reduced energy density and inadequate voltage utilization. Herein, a porous conductive graphene aerogel (GA) scaffold was decorated with copper cobalt selenide ((CuCo)Se₂) or iron selenide (FeSe₂) to construct positive and negative electrodes, respectively. The (CuCo)Se₂/GA and FeSe₂/GA electrodes exhibited high specific capacitances of 672 and 940 F g^-1, respectively, at 1 A g^-1. The capacitance contributions from the Co³⁺/Co₂⁺ and Fe³⁺/Fe²⁺ redox couple for the positive and negative electrodes were determined to elucidate the energy storage mechanism. Furthermore, the kinetics study of the two electrodes was performed, revealing b values ranging between 0.7 and 1 at various scan rates and demonstrating that the surface-controlled processes played the dominant role, leading to fast charge storage capability for both electrodes. Fabrication of an ASC device with a configuration of (CuCo)Se₂/GA//FeSe₂/GA resulted in a voltage of 1.6 V, a high energy density of 39 W h kg^-1, and a power density of 702 W kg^-1. The excellent electrochemical performances of the (CuCo)Se₂/GA and FeSe₂/GA electrodes demonstrate their potential applications in energy storage devices.