A novel approach
was introduced to remove metal (Ag+) ions from aqueous
solution and subsequently restate the metal-loaded
materials for a number of environmentally friendly applications. A
versatile adsorbent, polypyrrole with mercapto-functionalized chelating
groups (PPy/MAA), successfully adsorbed Ag+ ions through
subsequent reduction to silver nanoparticles (Ag0 NPs)
into the composite matrix. The as-prepared composite (PPy/MAA) and
Ag-adsorbed PPy/MAA (PPy/MAA/Ag0) were fully characterized
by FE-SEM, EDS, HR-(S)TEM, XRD, FTIR, BET, XPS, and zeta potential
measurements. Batch adsorption results showed that the adsorption
process can be explained well by a pseudo-second-order model. The
maximum adsorption capacity calculated using a Langmuir isotherm model
was 714.28 mg/g at 25 °C. XRD, XPS, and HR-TEM analyses confirmed
the presence of metallic silver nanoparticles on the surface of the
composite matrix after the in situ reduction of Ag+ to Ag0. Among the applications tested, the metal-loaded
waste (PPy/MAA/Ag0) was found to have antimicrobial activity,
as it inhibited the growth of Escherichia coli, while pure adsorbent without silver showed no killing effect toward E. coli. PPy/MAA/Ag0 also played an important
role in the catalytic reduction of 4-nitrophenol and also exhibited
good sensitivity to NO2 in gas-sensing applications. Therefore,
the developed PPy/MAA composite achieved 2-fold environmental benefits,
not only remediating Ag+ from polluted waterways but also
opening a new window for subsequently acting as an agent for antibacterial
ability, catalytic activity, and gas-sensing efficiencies.
In this paper, we present the first experimental evidence for electronic to protonic conduction switching in p-type semiconducting nanostructured cuprous oxide (Cu2O) porous films when exposed to humidity.
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