Search

Background Inkjet printing of graphene conductive inks plays a critical role in the technological advancement in flexible and stretchable electronics applications. In this study, water-based graphene conductive ink was fabricated and printed through inkjet printing on polyethylene terephthalate substrate. Methods Deionized (DI) water and three different types of surfactants (sodium dodecyl sulfate (SDS), polyvinylpyrrolidone (PVP), and Gum Arabic GA)) were utilized in the preparation of graphene conductive inks. Significant Finding Among other conductive ink formulations, graphene conductive inks fabricated using the DI/PVP surfactant exhibit relatively higher wetting and stability properties. In addition, this formulation led to an increment of about 80% in electrical conductivity compared to DI water-based conductive ink. The results revealed an improvement of about 50 times in the electrical conductivity of the printed film when the number of the printing cycle was increased from 1 to 10. Furthermore, it was observed that under 50% tensile strain, the graphene film prepared using the PVP surfactant exhibited only a 0.12% drop in electrical conductivity. Therefore, it is inferred that the conductive inks prepared from DI/PVP surfactants are highly suitable for use in flexible and wearable electronics.

The exfoliation of graphite is an intriguing approach for simple, fast and large-scale production of graphene. In the present study, three types of electrolytes were investigated, namely an ionic liquid (H2SO4), aqueous acid (H3PO4) and inorganic salt ((NH4)2SO4). Different sonication times (15, 30, 45 and 60 min) at room temperature were used to assist the electrochemical exfoliation. The graphene that was produced was characterized by the zeta potential, surface electrical conductivity, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, field emission microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). From the XRD analysis, it was observed that the graphene flakes had a broad peak centred at 26.5°, which corresponds to the (0 0 2) plane of graphene crystal. The FTIR spectrum revealed that the prominent peak was in conjunction with exfoliated graphene. The characteristic Raman bands were observed for the D, G and 2D bands and the ratio of I2D/IG was 1.7, which indicated that the exfoliated graphene was a multilayer structure. From the results, it was found that graphene obtained with the H2SO4 electrolyte that used a 45 min sonication time had the highest stability, best electrical conductivity, lowest crystallite size, fewer defects and lowest interlayer distance.

Silver nanoparticles (AgNPs) have been extensively studied for many decades due to their unique features and wide range of applications. In the present study, AgNPs were synthesized using methanolic leaf extracts from Imperata cylindrical by green method. Here, effect of silver nitrate (AgNO3) concentrations (0.5 mM, 0.7 mM and 0.9 mM) on the production of AgNPs was investigated. The synthesized AgNPs were verified by X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), zeta potential and surface electrical conductivity. The synthesized AgNPs were consisted of face centered cubic crystals as demonstrated from XRD studies. Surface plasmon resonance bands of AgNPs occurred in the wavelength range of 417-420 nm. AgNPs exhibit spherical shape and with sizes of 30 to 40 nm. Zeta potential values of AgNPs were -32 to -38 mV. It was found that increased concentration of AgNO3 resulted in increasing crystallite size and size of AgNPs. Surface electrical conductivity results showed that AgNO3 concentration 0.5 mM produced higher electrical conductivity 0.435×102 Sm-1 compared to those of 0.7 mM and 0.9 mM concentrations.

In the development of the flexible electronics industry, creating high stability and environmentally friendly conductive inks has remained a key challenge. In this study, less-toxic solvent exchange techniques graphene conductive inks were printed on polyethylene terephthalate substrate. This study aimed to investigate the properties of graphene conductive ink prepared by solvent exchange techniques using four combinations of solvents. To this end, four combinations of solvents were used to fabricate the graphene conductive inks, namely, dimethylformamide (DMF): xylene, DMF: toluene, DMF: ethanol, and DMF: acetone. Conductive ink fabricated by DMF: ethanol solvent exchange was produced with a higher degree of stability and wettability, as well as a 5% enhancement of electrical conductivity, in comparison with other solvent exchange solutions. The findings showed that the electrical conductivity of conductive film increased with an increase of 45% printing cycles. Furthermore, it has been observed that the electrical conductivity of printed graphene film decreased at only 0.02% even over 10 times of bending cycles. Therefore, the combination of DMF: ethanol solvent exchange is the most suitable formulation for graphene conductive inks.

Inkjet printing of conductive ink on flexible substrates is emerging as an attractive technology for wide variety applications. In this study, graphene and silver nanoparticles (AgNPs) conductive inks were printed on polyvinyl alcohol (PVA) substrates by inkjet printer. Effect of different solvents, printing cycles and annealing time on the performance of conductive ink was investigated. Three different groups of solvents were used to prepare the conductive ink; deionized water (DI): ethylene glycol (EG): glycol (G), isopropyl alcohol (IA): ethylene glycol (EG): glyceol (G) and dimethylformamide (DMF): Ethylene glycol (EG): Glyceol (G). DMF: EG: G solutions produced conductive ink with higher stability, wettability and electrical conductivity compared to other conductive ink formulations. It was observed that increased of printing cycles (from 1 to 5) times and annealing time (from 0 to 30) min had increase the electrical conductivity. During stretching, graphene conductive ink on PVA substrate shows lower electrical conductivity reduction compared to that of AgNPs conductive ink. Flaky shape of graphene able to maintain the conductive paths under loading condition.

In this study, Graphene has been synthesized by using electrochemical exfoliation method. Effect of sonication times (15, 30 and 45 min) at room temperature on the production of graphene was investigated. The synthesized graphene were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Atomic Force Microscopy (AFM). The crystal structure of the exfoliated graphene were analyzed using XRD. The graphene flakes exhibit a sharp peak centered at 26.5°corresponding to the (002) plane of graphene crystal. It is found that, the crystallite sizes is gradually decreased with increased in sonication time. The FTIR spectrum reveals the prominent appearance of C-O-H group which indicate that OH− radicals exist in conjunction with exfoliated graphene sheets. Graphene flakes with average thickness of 0.2 nm to 0.8 nm were observed using AFM. The electrical conductivity results showed that 45 min sonication time produced the highest electrical conductivity (1.38×102sm−1).