ABSTRACT
Ammonia is one of the most frequently produced chemicals in the world, and thus, reliable measurements of different NH3 concentrations are critical for a variety of industries, among which are the agricultural and healthcare sectors. The currently available technologies for the detection of NH3 provide accurate identification; however, they are limited by size, portability, and fabrication cost. Therefore, in this work, we report the laser-induced forward transfer (LIFT) of single-walled carbon nanotubes (SWCNTs) decorated with tin oxide nanoparticles (SnO2 NPs), which act as sensitive materials in chemiresistive NH3 sensors. We demonstrate that the LIFT-fabricated sensors can detect NH3 at room temperature and have a response time of 13 s (for 25 ppm NH3). In addition, the laser-fabricated sensors are fully reversible when exposed to multiple cycles of NH3 and have an excellent theoretical limit of detection of 24 ppt.
ABSTRACT
The increasing amount of residual pharmaceutical contaminants in wastewater has a negative impact on both the environment and human health. In the present study, we developed new cellulose acetate/Mg-Al layered double hydroxide (Mg-Al LDH) nanocomposite membranes as an efficient method to remove pharmaceutical substances from wastewater. The morphology, porosity, surface properties and thermal stability of nanocomposite membranes containing various amounts of nanofiller were evaluated by scanning electron microscopy (SEM), X-ray microtomography (µCT), contact angle measurements and thermogravimetric analysis (TGA). The Mg-Al LDH nanofiller showed a high degree of exfoliation in the polymer matrix, evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hydrodynamic properties and adsorption capacity were evaluated with pure water and aqueous solutions of two common drugs, diclofenac sodium (DS) and tetracycline (TC), and the nanocomposite membranes showed an improved permeability compared with neat cellulose acetate. The membrane prepared with 4 wt.% Mg-Al LDH loading exhibited the highest water flux compared with the pure polymer one (529 vs 36 L·m-2·h-1) and a tenfold increase in adsorption capacity for DS. This enhancement is attributed to electrostatic interactions between the negatively charged drug molecule and positively charged Mg-Al LDH layers. Conversely, in the case of TC, the increase in adsorption capacity was smaller and was assigned to hydrogen bonding interactions between the drug molecule and the nanofiller.
