Isotope labelling experiments were performed to trace the nitrogen source of
ammonia. In one set of experiments,
15 N labelling was conducted for pyridinium
chloride leading to the formation of
14
NH 3 ammonia. In the other set, labelled
15 N 2
gas was used for the nitrogen reduction under light illumination. Figure 6.13c
presents the NMR results collected on standard [
15 NH 4 ]
+ solution and labelled
15 N 2
samples, respectively. In both cases, the characteristic peaks (J = 72 Hz) corresponding to the
15 N–
1 H coupling are observed. Thus, the nitrogen source of
ammonia is proved to nitrogen gas. This study illustrates the photocatalytic activity
of the biomimetic FeMoS-chalcogels with FeMoS clusters as active sites. The
FeMoS-chalcogels improves the original catalytic properties of nitrogenases by
enabling strong white light absorption.
6.4 Other Inorganic Gels
Pal and co-workers prepared an AgVO 3 inorganic gel without using any carboncontaining gelators (Fig. 6.14). The preparation for AgVO 3 hydrogel starts by
mixing the aqueous solutions of AgNO 3 and NH 4 VO 3 . As a result of dipole–dipole
interactions, AgVO 3 molecules are produced leading to the formation of a
cross-linked molecular network. Following encapsulation of water molecules
within the networks, AgVO 3 hydrogel is successfully prepared. The resulting
AgVO 3 hydrogel exhibits prominent adsorption for methylene blue (MB). As
shown in Fig. 6.14b, an aqueous solution contaminated with MB is placed on the
top of the AgVO 3 hydrogel. Prior to adsorption, the upper solution is in dark blue
showing a high concentration of MB in water. After 48 h, the colours of the AgVO 3
hydrogel and upper solution change significantly (Fig. 6.14b). By tracing the
concentration of MB in the upper solution using UV-Vis spectroscopy, the MB
adsorption capacity for per unit amount of AgVO 3 hydrogel was determined to
reach 580 mg g
−1 . In addition to organic dye removal, the AgVO 3 hydrogel is also
capable for heavy metal removal. Instead of placing a MB-contaminated aqueous
solution, a solution containing HgCl 2 or Na 3 AsO 4 salts were also tested. For both of
the contaminants, the AgVO 3 hydrogel acts as an effective sorption matrix for the
hazardous waste removal.
Another example of inorganic gels is vanadium oxide (V 2 O 5 ÁnH 2 O) hydrogel,
which comprises nanoribbons formed by the non-covalent cross-linking of vanadium oxide [43–45]. The size of the nanoribbons formed by cross-linked vanadium
oxide is about over 1 µm long and 10 nm wide [46]. The unique properties of
vanadium oxide and the intrinsic porosity of the hydrogel enable a wide range of
applications including self-cleaning, biological sensing and drug delivery [47, 48].
Further to inorganic AgVO 3 and V 2 O 5 hydrogels, Fernandez and co-workers
developed a composite hydrogel by mixing two solutions containing silver vanadium oxide (b-AgVO 3 ) and slightly reduced vanadium oxide (V 1.6
5+ V 0.4
4+ O 4.8 ),
respectively [49]. By varying the ratio and concentrations of the two components, a
range of composite hydrogels can be prepared. Examples include H1A10; the
204
6 Inorganic Gels
ammonia. In one set of experiments,
15 N labelling was conducted for pyridinium
chloride leading to the formation of
14
NH 3 ammonia. In the other set, labelled
15 N 2
gas was used for the nitrogen reduction under light illumination. Figure 6.13c
presents the NMR results collected on standard [
15 NH 4 ]
+ solution and labelled
15 N 2
samples, respectively. In both cases, the characteristic peaks (J = 72 Hz) corresponding to the
15 N–
1 H coupling are observed. Thus, the nitrogen source of
ammonia is proved to nitrogen gas. This study illustrates the photocatalytic activity
of the biomimetic FeMoS-chalcogels with FeMoS clusters as active sites. The
FeMoS-chalcogels improves the original catalytic properties of nitrogenases by
enabling strong white light absorption.
6.4 Other Inorganic Gels
Pal and co-workers prepared an AgVO 3 inorganic gel without using any carboncontaining gelators (Fig. 6.14). The preparation for AgVO 3 hydrogel starts by
mixing the aqueous solutions of AgNO 3 and NH 4 VO 3 . As a result of dipole–dipole
interactions, AgVO 3 molecules are produced leading to the formation of a
cross-linked molecular network. Following encapsulation of water molecules
within the networks, AgVO 3 hydrogel is successfully prepared. The resulting
AgVO 3 hydrogel exhibits prominent adsorption for methylene blue (MB). As
shown in Fig. 6.14b, an aqueous solution contaminated with MB is placed on the
top of the AgVO 3 hydrogel. Prior to adsorption, the upper solution is in dark blue
showing a high concentration of MB in water. After 48 h, the colours of the AgVO 3
hydrogel and upper solution change significantly (Fig. 6.14b). By tracing the
concentration of MB in the upper solution using UV-Vis spectroscopy, the MB
adsorption capacity for per unit amount of AgVO 3 hydrogel was determined to
reach 580 mg g
−1 . In addition to organic dye removal, the AgVO 3 hydrogel is also
capable for heavy metal removal. Instead of placing a MB-contaminated aqueous
solution, a solution containing HgCl 2 or Na 3 AsO 4 salts were also tested. For both of
the contaminants, the AgVO 3 hydrogel acts as an effective sorption matrix for the
hazardous waste removal.
Another example of inorganic gels is vanadium oxide (V 2 O 5 ÁnH 2 O) hydrogel,
which comprises nanoribbons formed by the non-covalent cross-linking of vanadium oxide [43–45]. The size of the nanoribbons formed by cross-linked vanadium
oxide is about over 1 µm long and 10 nm wide [46]. The unique properties of
vanadium oxide and the intrinsic porosity of the hydrogel enable a wide range of
applications including self-cleaning, biological sensing and drug delivery [47, 48].
Further to inorganic AgVO 3 and V 2 O 5 hydrogels, Fernandez and co-workers
developed a composite hydrogel by mixing two solutions containing silver vanadium oxide (b-AgVO 3 ) and slightly reduced vanadium oxide (V 1.6
5+ V 0.4
4+ O 4.8 ),
respectively [49]. By varying the ratio and concentrations of the two components, a
range of composite hydrogels can be prepared. Examples include H1A10; the
204
6 Inorganic Gels