furthermore considerably, due to their large surface area and properly-defined porous structure, mesoporous metal oxides, which include ZnO, SnO₂, TiO₂, WO₃, have become increasingly interested in gas sensing reactions, which offer many exposed active sites to have interaction with target gas and opens channels for the rapid diffusion and penetration of gas molecules. another case as newly emerging colorimetric materials for visual sensing applications, metal-organic frameworks(MOF) with adjustable colorimetric responses can be considered consistent with the design capability of MOF structures, kinds of MOFs with colorimetric properties acquire customizable via unique design and synthesis. MOFs are highly porous crystalline extended structures composed of metal clusters (or cations) with coordinated to organic ligands in an ordered pattern[329]. MOFs containing transition metal ions including iron, cobalt, copper, zinc, cadmium, and zirconium generally display color changes and tunable colorimetric behavior in response to various target analytes. target analytes adsorbed by MOFs with open metal sites can change the coordinate environment around the center of the metal ion, and a change in the d-d ion transfer of the metal ion can cause a visible color change. in comparison to discrete metal ions or chromophores as colorimetric probes, MOFs have advanced structural stability because of their coordination network. placing chromophores in voids or on MOF surfaces is another manner to design colorimetric materials. Such chromophore / MOF structures additionally show more stability because of the protection supplied through the framework within the chromogenic reaction. further, intrinsic porosity, open metal sites, and Lewis acid/base sites MOFs can accommodate and preconcentrate guest analysis, hence increasing detection sensitivity. similarly, the rational adjustment of MOF pore size for the adsorption and separation of small guest molecules via size-exclusion effects permits selective detection of particular targets. eventually, MOFs can be effortlessly converted to film on numerous hard or flexible layers with suitable uniformity due to their crystalline nature, which could be very beneficial for making sensing devices. because of the above advantages, MOF-based colorimetric measurement systems have outstanding stability, sensitivity, selectivity, and simplicity of assembly, and we can be optimistic that MOFs with tunable colorimetric properties should have a brilliant future in sensing applications [330, 331].
furthermore
considerably
, due to their large surface area and
properly
-defined porous
structure
,
mesoporous
metal
oxides, which include
ZnO
, SnO₂, TiO₂, WO₃, have become
increasingly
interested in gas
sensing
reactions, which offer
many
exposed active
sites
to have interaction with
target
gas and opens channels for the rapid diffusion and penetration of gas molecules.
another
case as
newly
emerging colorimetric materials for visual
sensing
applications, metal-organic frameworks(MOF) with adjustable colorimetric responses can
be considered
consistent with the design capability of MOF
structures
, kinds of
MOFs
with colorimetric properties acquire customizable via unique design and synthesis.
MOFs
are
highly
porous crystalline extended
structures
composed of
metal
clusters (or cations) with coordinated to organic ligands in an ordered pattern[329].
MOFs
containing transition
metal
ions including iron, cobalt, copper, zinc, cadmium, and zirconium
generally
display color
changes
and tunable colorimetric behavior in response to various
target
analytes.
target
analytes adsorbed by
MOFs
with open
metal
sites
can
change
the coordinate environment around the center of the
metal
ion, and a
change
in the d-d ion transfer of the
metal
ion can cause a visible color
change
.
in
comparison to discrete
metal
ions or
chromophores
as colorimetric probes,
MOFs
have advanced structural stability
because
of their coordination network.
placing
chromophores
in voids or on MOF surfaces is another manner to design colorimetric materials. Such
chromophore
/ MOF
structures
additionally
show
more stability
because
of the protection supplied through the framework within the
chromogenic
reaction.
further
, intrinsic porosity, open
metal
sites
, and Lewis acid/base
sites
MOFs
can accommodate and
preconcentrate
guest analysis,
hence
increasing detection sensitivity.
similarly
, the rational adjustment of MOF pore size for the adsorption and separation of
small
guest molecules via size-exclusion effects permits selective detection of particular
targets
.
eventually
,
MOFs
can be
effortlessly
converted to film on numerous
hard
or flexible layers with suitable uniformity due to their crystalline nature, which could be
very
beneficial for making
sensing
devices.
because
of the above advantages, MOF-based colorimetric measurement systems have outstanding stability, sensitivity, selectivity, and simplicity of assembly, and we can be optimistic that
MOFs
with tunable colorimetric properties should have a brilliant future in
sensing
applications [330, 331].