Spray-coated Carbon Nanotube Research Articles

Flexible Screen-Printed Amperometric Sensors Functionalized With Spray-Coated Carbon Nanotubes and Electrodeposited Cu Nanoclusters for Nitrate Detection

In this work, we present a novel, sensitive, easy-to-fabricate, flexible amperometric sensor constituted by screen-printed silver (Ag) electrodes functionalized with a copper (Cu) film electrodeposited on top of a spray coated network of single-walled carbon nanotubes (SWCNTs). The Cu/SWCNTs/Ag electrode showed excellent catalytic activity towards the electro-reduction of nitrate ions at neutral pH with a significant increase in cathodic peak currents in comparison with the electrode without SWCNTs (Cu/Ag). The developed Cu/SWCNTs/Ag sensor showed a wide linear detection range from 0.5 μM to 6.0 mM (0.31 mg/l to 372.02 mg/l) with good sensitivity (18.39 μA/mM) and a calculated limit of detection (LOD) of 0.166 nM (10.29 μg/l). It also showed a good selectivity (maximum standard deviation (SD) was 3.25 μA) towards different interfering ions (Fe2+, Na+, Cu2+, SO42-, CH3COO-, Cl-, NO2- and HCO3-), as well as good reproducibility, mechanical durability, time and temperature stability. In real sample analysis (tap and river water), the sensor exhibited good agreement with the compared outcome of high-performance liquid chromatography (HPLC) measurements, proving to be a promising analytical tool for the detection of nitrate in water.

High-output, transparent, stretchable triboelectric nanogenerator based on carbon nanotube thin film toward wearable energy harvesters

Self-powered electronics can improve wearable health monitoring systems. Triboelectric generation, a type of energy harvesting technology, is a promising candidate as power source for wearable devices by generating electricity from body motion. For wearable energy harvesters, stretching is required for adaptation to dynamic three-dimensional body motions, and sufficient output power should be delivered for driving electronic devices. However, the currently demonstrated output power remains insufficient for using stretchable triboelectric generation in practice. We propose high-output (8 W/m2), stretchable triboelectric generators based on transparent carbon nanotube thin films. We realize high output by the surface treatment with fluorine plasma as well as stretchability by scalable and cost-effective spray coated carbon nanotube thin films. The carbon nanotube films also provide excellent scalability, optical transparency (95% transmittance), and durability under large deformations of tensile strain up to 80%. We also demonstrate applications to self-powered optical wireless communication sheets and gloves, where blue light emitting diodes are embedded in the triboelectric nanogenerator sheet and wired using stretchable carbon nanotube films. Our stretchable energy harvesting sheets can contribute to solve major problems in wearable electronics (i.e., power source limitations) at low cost.

Crack-Tolerant Metal Composites as Photovoltaic Gridlines

Multiwalled carbon nanotubes are used to electromechanically reinforce metal gridlines and busbars on commercial triple-junction solar cells. For the reinforcement, we create a layer-by-layer microstructure which consists of electroplated silver, spray-coated carbon nanotubes, and another layer of electroplated silver. The top silver layer is intercalated through the network of carbon nanotubes, connecting with the bottom silver layer. This metal matrix composite integration leads to beginning-of-life cell performance identical to the control cells with conventional metallization. Fill factor and efficiency remain the same. When the cells are intentionally cracked, the composite-reinforced cells maintain superior performance compared with the control cells. The key difference is that short-circuit current density of composite-reinforced cells remains essentially unaffected, whereas a reduction >50% is observed for the control cells. The metal matrix composites show strong potential to improve the reliability and service time of space photovoltaics against stress-induced fractures.

High-Performance Thin-Film Composite Membrane with an Ultrathin Spray-Coated Carbon Nanotube Interlayer

We fabricated a thin-film composite (TFC) forward osmosis (FO) membrane with an ultrathin spray-coated carbon nanotube (CNT) interlayer. The impact of the CNT interlayer on the polyamide (PA) layer structural properties and transport behavior in FO were investigated. Results indicate that the CNT interlayer provides an interface which enables the formation of a highly permeable and selective PA layer with a large effective surface area for water transport, while inhibiting the formation of a flower-like PA structure inside the substrate pores. The TFC-FO membrane with the CNT interlayer exhibited a much greater water flux than previously reported for FO membranes, while maintaining comparable salt rejection. Specifically, a membrane perm-selectivity or ratio of water (A) to salt permeability coefficients (B) (A/B value) of 39 bar–1 was achieved for the TFC-PA-CNT membrane. Implications of the results for the fabrication of high-performance TFC-FO membranes are further discussed.

Spray-coated carbon nanotube carpets for creeping reduction of conducting polymer based artificial muscles

During cyclic actuation, conducting polymer based artificial muscles are often creeping from the initial movement range. One of the likely reasons of such behaviour is unbalanced charging during conducting polymer oxidation and reduction. To improve the actuation reversibility and subsequently the long time performance of ionic actuators, we suggest using spray-coated carbon nanotube (CNT) carpets on the surface of the conducting polymer electrodes. We show that carbon nanotubes facilitate a conducting polymer redox reaction and improve its reversibility. Consequently, in the long term, charge accumulation in the polymer film is avoided leading to a significantly improved lifetime performance during cycling actuation. To our knowledge, it is the first time a simple solution to an actuator creeping problem has been suggested.

Behaviour of one-step spray-coated carbon nanotube supercapacitor in ambient light harvester circuit with printed organic solar cell and electrochromic display

A printed energy harvesting and storage circuit powered by ambient office lighting and its use to power a printed display is reported. The autonomous device is composed of three printed electronic components: an organic photovoltaic module, a carbon-nanotubes-only supercapacitor and an electrochromic display element. Components are fabricated from safe and environmentally friendly materials, and have been fabricated using solution processing methods, which translate into low-cost and high-throughput manufacturing. A supercapacitor made of spray-coated carbon nanotube based ink and aqueous NaCl electrolyte was charged using a printed organic photovoltaic module exposed to office lighting conditions. The supercapacitor charging rate, self-discharge rate and display operation were studied in detail. The supercapacitor self-discharge rate was found to depend on the charging rate. The fully charged supercapacitor was used as a power source to run the electrochromic display over 50 times.

Scalable nanomanufacturing of surfactant-free carbon nanotube inks for spray coatings with high conductivity

Spray-coated carbon nanotube films offer a simple and printable solution for fabricating low cost, lightweight, and flexible thin-film electronics. However, current nanotube spray inks require either a disruptive surfactant or destructive surface functionalization to stabilize dispersions at the cost of the electrical properties of the deposited film. We demonstrate that high-purity few-walled carbon nanotubes may be stabilized in isopropanol after surface functionalization and that optimizing the ink stability dramatically enhances the conductivity of subsequent spray-coated thin films. We consequently report a surfactant-free carbon nanotube ink for spray-coated thin films with conductivities reaching 2,100 S/cm. Zeta-potential measurements, used to quantify the nanotube ink dispersion quality, directly demonstrate a positive correlation with the spraycoated film conductivity, which is the key metric for high-performance printed electronics.

Fabrication of Dye Sensitized Solar Cells with Spray Coated Carbon Nano Tube (CNT) Based Counter Electrodes

Abstract In this paper, dye-sensitized solar cells (DSSC) have been fabricated on fluorine-tin-oxide (FTO) glass substrates, in which TiO 2 electrodes have been printed and multi-walled carbon nanotubes (CNT) counter electrodes have been spray-coated. Ruthenium based dye (C 58 H 86 N 8 O 8 RuS 2 ) has been used as photosensitizer, and the cell was constructed by stacking the dye-sensitized TiO2 on CNT counter electrodes using Surlyn sheet of 50 μm thick as a spacer. The electrolyte containing I-/I3- redox couple was then injected into the cell structure before the spacer was sealed and heat pressed. From the study of the cell I-V characteristics, it showed that that the light energy conversion efficiency increased with decreasing light transmittance and sheet resistances of the CNT counter electrodes, and is lower compared to efficiency from similar cells Pt counter electrodes.

Absorptive carbon nanotube electrodes: consequences of optical interference loss in thin film solar cells.

A current bottleneck in the thin film photovoltaic field is the fabrication of low cost electrodes. We demonstrate ultrasonically spray coated multiwalled carbon nanotube (CNT) layers as opaque and absorptive metal-free electrodes deposited at low temperatures and free of post-deposition treatment. The electrodes show sheet resistance as low as 3.4 Ω □(-1), comparable to evaporated metallic contacts deposited in vacuum. Organic photovoltaic devices were optically simulated, showing comparable photocurrent generation between reflective metal and absorptive CNT electrodes for photoactive layer thickness larger than 600 nm when using archetypal poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61-butyric acid methyl ester (PCBM) cells. Fabricated devices clearly show that the absorptive CNT electrodes display comparable performance to solution processed and spray coated Ag nanoparticle devices. Additionally, other candidate absorber materials for thin film photovoltaics were simulated with absorptive contacts, elucidating device design in the absence of optical interference and reflection.

Spray-coated carbon nanotube thin-film transistors with striped transport channels

We present results for the transfer characteristics of carbon nanotube thin-film transistors (CNT-TFTs) that utilize single-walled carbon nanotube thin-films prepared by direct spray-coating on the substrate. By varying the number of spray-coatings (Nsp) and the concentration of nanotubes in solution (CNT), it was possible to control the conductivity of the spray-coated nanotube thin-film from 129 to 0.1 kΩ/□. Also, by introducing stripes into the channel of the CNT-TFT, and thereby reducing the number of metallic percolation paths between source and drain, it was possible to enhance the on/off current ratio 1000-fold, from 10 to 104, demonstrating that it may be possible to utilize spray-coating as a method to fabricate CNT-TFTs for large area switching array applications.

Spray-coated Carbon Nanotube Counter Electrodes for Dye-sensitized Solar Cells

Carbon Nanotube(CNTs) counter electrode is a promising alternative to Platinum counter electrode for dye sensitized solar cells (DSSCs). In this study, CNT counter electrodes having different visible light transmittance were prepared on fluorine-doped tin oxide (FTO) glass surface by spray coating method. Microstructural images show that there are CNT-tangled region coated on FTO glass counter electrodes. Using such CNT counter electrodes and screen printed electrodes, DSSCs were assembled and its I-V characteristics have been studied and compared. Light energy conversion efficiency of DSSCs increased with decreasing in light transmittance of CNT counter electrode. Efficiency of DSSCs having CNT counter electrode is compatible to that of Pt counter electrode.