Combinatorial and High-Throughput Screening of Materials ...

ACS Combinatorial Science
REVIEW
Figure 32. Schematic description of a C/HT workflow developed for the research and development of hybrid organic
sol gel processing. 314
inorganic coatings based on
fabrication methods have been reported as summarized in
Table 4. 316 344 Aspecific type of library layout depends on the
required density of space to be explored, available library-fabrication
capabilities, and capabilities of high-throughput characterization
techniques. Upon array fabrication, the array is exposed to an
environment of interest and steady-state or dynamic measurements
are acquired to assess materials performance. Serial scanning
mode of analysis (e.g., optical or impedance spectroscopies) is
often performed to provide more detailed information about
materials property over parallel analysis (e.g., imaging). When
monitoring a dynamic process (e.g., response/recovery time,
aging) of sensing materials arranged in an array with a scanning
system, the maximum number of elements in sensor library that
can be measured with the required temporal resolution can be
limited by the data-acquisition ability of the scanning system. 338 In
addition to measurements of materials performance parameters, it
is important to characterize intrinsic materials properties. 40 Combinatorial
development of sensing materials can be categorized
based on sensors that utilize various energy-transduction principles
for their operation that involve radiant, mechanical, and electrical
types of energy.
3.4.1. Materials for Sensors Based on Radiant Energy Transduction.
Sensors based on radiant energy transduction can be
categorized on the basis of the five parameters that completely
describe a lightwave, such as its amplitude, wavelength, phase,
polarization state and time dependent waveform. The majority of
the developed sensing materials for these types of sensors rely on
the formulated colorimetric and fluorescent materials and intrinsically
conducting polymers.
Optimizing formulated sensor materials is a cumbersome
process because theoretical predictions are often limited by
practical issues, such as poor solubility and compatibility of
formulation components. 319,345 347 These practical issues
represent significant knowledge gaps that prevent a more
efficient rational design of formulated sensor materials. Thus,
combinatorial methods have been employed for the development
of multicomponent formulated sensor materials for
gaseous 319,329,348,349 and ionic 320,337,338,350,351 species.
Applying polymers with an intrinsic conductivity also permits
development of chemical and biological sensors based on radiant
energy transduction. 352 356 A variety of conjugated organic
monomers readily undergo polymerization and form linear
polymers. For example, acetylene, p-phenylenevinylene, p-phenylene,
pyrrole, thiophene, furane, and aniline form conducting
polymers that are widely employed in sensors. 353,357 359 However,
as prepared, conducting polymers lack selectivity and often
are unstable. Thus, such polymers are chemically modified to
reduce these undesirable effects. Modification methods include
side-group substitution of heterocycles, doping of polymers,
charge compensation upon polymer oxidation by incorporation
of functionalized counterions, formation of organic inorganic
hybrids, incorporation of various biomaterials (e.g., enzymes,
antibodies, nucleic acids, cells), and others. 357,360,361 Variations
in polymerization conditions (e.g., oxidation potential, oxidant,
temperature, solvent, electrolyte concentration, monomer concentration,
etc.) can be also employed to produce diverse
polymeric materials from the same monomer because polymerization
conditions affect sensor-related polymers properties
610 dx.doi.org/10.1021/co200007w |ACS Comb. Sci. 2011, 13, 579–633