RESUMO
This study presents graphene inks produced through the liquid-phase exfoliation of graphene flakes in water using optimized concentrations of dispersants (gelatin, triton X-100, and tween-20). The study explores and compares the effectiveness of the three different dispersants in creating stable and conductive inks. These inks can be printed onto polyethylene terephthalate (PET) substrates using an aerosol jet printer. The investigation aims to identify the most suitable dispersant to formulate a high-quality graphene ink for potential applications in printed electronics, particularly in developing chemiresistive sensors for IoT applications. Our findings indicate that triton X-100 is the most effective dispersant for formulating graphene ink (GTr), which demonstrated electrical conductivity (4.5 S·cm-1), a high nanofiller concentration of graphene flakes (12.2%) with a size smaller than 200 nm (<200 nm), a low dispersant-to-graphene ratio (5%), good quality as measured by Raman spectroscopy (ID/IG ≈ 0.27), and good wettability (θ ≈ 42°) over PET. The GTr's ecological benefits, combined with its excellent printability and good conductivity, make it an ideal candidate for manufacturing chemiresistive sensors that can be used for Internet of Things (IoT) healthcare and environmental applications.
RESUMO
An aerosol jet printing (AJP) process for depositing ruthenium dioxide (RuO2) as a promising material for pH sensing is reported. Graphene oxide (GO) with a large surface area was used for the in situ sol-gel deposition of RuO2 nanoparticles on its surface. The cosolvent ratio and solid loading of the solution are adjusted to form a printable and stable ink. The monodispersed aerosol was atomized on the surface of the screen-printed carbon electrode in order to develop an integrated pH sensor. The RuO2-GO pH sensor demonstrates excellent performance, with a rapid response time of less than 5 s and high sensitivity in the pH range of 4-10. Compared to traditional carbon electrodes, the RuO2-GO sensor shows up to four times higher sensitivity. The increased sensitivity is a result of the consistent attachment of small-crystallized RuO2 nanoparticles onto the surface of GO sheets, leading to a synergistic effect. Thanks to the AJP method as a facile and cost-effective integration technique, the fabricated electrodes can serve as an alternative to traditional rigid pH electrodes for accurate pH measurement.
RESUMO
Tunable mesoporosity and nanoporosity of stimuli pH-responsive (N-vinyl imidazole-ran-acryloylmorpholine) hydrogels studied in terms of %swelling at various ionic strength, pH, temperature, and crosslinker concentration values were investigated. Hydrogel properties including diffusional exponent, number of links between two crosslinks, rms end-to-end distance and mesh size of gels were evaluated. The structural sequence of the scaffolds was tested and verified using Kelen-Tudos technique, and Alfrey-Price relationship. Hydrogels were characterized using FTIR, thermogravimetric analysis, differential scanning calorimetry, and freeze-dried Scanning electron micrographs techniques. The reversible pH responsiveness and possible mesoporous and nanoporous (i.e., 0.88-4.03 nm) structures suggest their suitable candidate in membrane technology and/or is an adequate drug delivery vehicle in drug delivery systems.