Chemical
sensors
based on mesoporous silica nanotubes (MSNTs) for
the quick detection of Fe(III) ions have been developed. The nanotubes’
surface was chemically modified with phenolic groups by reaction of
the silanol from the silica nanotubes surface with 3-aminopropyltriethoxysilane
followed by reaction with 3-formylsalicylic acid (3-fsa) or 5-formylsalicylic
acid (5-fsa) to produce the novel nanosensors. The color of the resultant
3-fsa-MSNT and 5-fsa-MSNT sensors changes once meeting a very low
concentration of Fe(III) ions. Color changes can be seen by the naked
eye and tracked with a smartphone or fluorometric or spectrophotometric
techniques. Many experimental studies have been conducted to find
out the optimum conditions for colorimetric and fluorometric determining
of the Fe(III) ions by the two novel sensors. The response time, for
the two sensors, that is necessary to achieve a steady spectroscopic
signal was less than 15 s. The suggested methods were validated in
terms of the lowest limit of detection (LOD), the lowest limit of
quantification (LOQ), linearity, and precision according to International
Conference on Harmonization (ICH) guidelines. The lowest limit of
detection that was obtained from the spectrophotometric technique
was 18 ppb for Fe(III) ions. In addition, the results showed that
the two sensors can be used eight times after recycling using 0.1
M EDTA as eluent with high efficiency (90%). As a result, the two
sensors were successfully used to determine Fe(III) in a variety of
real samples (tap water, river water, seawater, and pharmaceutical
samples) with great sensitivity and selectivity.