200 ppb. Sensor color change. Detectable. [Hg(II)ion]. [HgII-Probe]n+. Binding Spectra ... part-per-billion (ppb) concentrations, according to World Health.
Mesoporous Sensors for Water Purification from Toxic Metals Materials Research Laboratory for Environmental & Energy Sherif A. El-Safty, Ahmed Shahat, Wojciech Warkocki
Considerable amounts of chemical and bioactive
capacity to serve as ion-preconcentrators with efficient reusability
contaminants were released into the environment and water
up to 20 repeated cycles (Fig. 3). The ion-selective workability for
sources from the industrial wastes. Standards for drinking water
optical sensor over multi-ion competitive species led to design of
have been revised several times creating the need for efficient
cost-alternative tool to current laboratory sensing methods. Mes-
adsorbent of the pollutants. It should be effective even at
oporous optical sensor can ultimately be employed in the basic
part-per-billion (ppb) concentrations, according to World Health
laboratory assays, in the measurement fields through portable
Organization (WHO).
devices, and in the household use as commercial indicators.
Here, our optical mesoporous sensors show ability to
The development of these technologies will open new
create sensing systems with indoor and outdoor responses and
opportunity for environmental cleanup, in the world. In this en-
with revisable, selective and sensitive recognition of toxic metals
deavor, we introduce an attractive means of pollution monitoring
down to part-per-trillion (ppt), in rapid sensing responses. The
by the use of simple, inexpensive, rapid responsive and portable
fabrication of nanosensor arrays based on the dense pattern
mesoporous sensors.
of surface functionality and adsorption of the colorant probe dopants with maintaining of the intrinsic mobility and flexibility into the nanoscale ordered materials enabled the development of [HgII-Probe]n+ Binding Spectra
sensing systems in which high flux of the target metals across the colorant is rapidly achieved within 30 seconds (Fig. 1). Indeed, monodispersed porosity in the range of 2–30 nm, and a large surface area (1000 m2/g) show promise of a new class of sensor materials. An attempt demonstrated here is the tailoring of colorant
0.3
A, a.u. At λ=550 nm
our ordered mesoporous materials that have a uniformly-sized,
Sensor color change
200 ppb 150 100 75 50 25 10 2.0 0.0
0.2
200 ppb
100 ppb
50 ppb
0.1
probe “azo-chromophore” in compact mesopore membranediscs, as optical sensor for visual detection of ultra trace
Detectable [Hg(II)ion]
10 ppb
Hg II
Sensor
ions (~ppt) (Fig. 2) using "low-tech" UV.Vis instrumentation.
0.0 450
However, brilliant colour transitions at the same frequency as the human eye could be recognized over a wide-range of Hg II concentrations. Moreover, the mesoporous sensors had the
500
550
600
650
700
λ, nm
Fig.1 Colour transition map and reflectance spectra observed for mesoporous HgII ion-sensor membrane with increasing concentrations of HgII ions from 2ppp to 200 ppb, at pH of 7.
Ordered Mesopores
Sensor formation
AzoProbe
2+
Hg .2A
-
ment Arrange Sensor Optical ction or Intera al Sens Chemic
Mesopore surface
Hg(II) ion-sensors
Sensor Array
AzoProbe
International 2010. Vol.8 No.2
Pure water
Probe
Mesopore sensor Hg2+ .2A -
Hg
2+
Na
+
Mg +
K
(I)
(II)
2+
(III)
Toxic water with Hg(II)
Toxic 2+ Hg
Optical Sensor
Fig.1 Fig. 1 Simple design of optical mesoporous sensor for toxic Hg(II) ions by the chemical construction of “azo-chromophore” with adjacent silanol group at pore surfaces to form well-arrangement azo-probe onto the nanoscale ordered materials. Note: azoprobe formula is 4-dodecyl-6-(2-pyridylazo) phenol
06
HgII optical sensor
(IV)
Sensor Array
Fig.1 Simple design for water treatment system from toxic Hg(II) ion using optical sensor arrays at complete stages of analyses of (I)optical ion-selective system, (II) removal of toxic ions, (III)extraction of toxic ions, and (IV) reusability of the sensor using C2O42- anions as a stripping agents.
