Topics in Current Chemistry (2020) 378:28
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a target-recognition process when it is irradiated by light of a suitable wavelength.
PEC sensing analysis is more sensitive and has a lower background than traditional
electrochemical and optical detection techniques because it separates the excitation
source (light) from the output signal (photocurrent). Because of its low cost, high
sensitivity, very low background noise, short response time, ease of use, and ability
to be miniaturized, PEC biosensing has rapidly been applied in various contexts,
including for food detection, environmental monitoring, gene testing, and early clinical diagnosis [1–3].
Electrochemiluminescence (ECL)—electrogenerated chemiluminescence—can
be considered the reverse of PEC. ECL is the electrochemical process in which an
excited species is electrogenerated at an electrode surface and then allowed to relax
to a less excited state, resulting in the emission of light. As it is a combined electrochemical and spectroscopic technique, ECL permits both spectral and temporospatial resolution, which makes it a powerful tool for both sensing and imaging [4, 5].
The literature on ECL biosensing methods is extensive, which reflects their inherent advantages, including rapidity, simplicity, high sensitivity, low cost, and nearzero background signal. The integration of nanotechnology into ECL biosensors has
also significantly enhanced the sensitivity and diversity of ECL biosensors in recent
years [6].
TiO 2 nanomaterials are commonly used in PEC and ECL biosensors due to their
advantageous properties, such as strong light absorption, chemical and mechanical stability, good catalytic ability, high biocompatibility, and large specific surface
areas [7, 8]. There are three crystalline forms of TiO 2 : anatase, rutile, and brookite. The utilization of TiO 2 nanomorphologies such as nanosheets [9], nanopillars
[10], nanoarrays [11], nanoparticles [12], nanorods [13], nanowires [14], nanoneedles [15, 16], nanoflowers [17], nanocubes [18], and mesocrystals [19, 20] in many
advanced bioanalytical strategies is frequently reported.
In this mini review, we present recent advances in PEC and ECL biosensing
based on TiO 2 nanomaterials, exploring in detail the sensing strategies used and
response mechanisms involved. However, given the limited space available in a mini
review, we concentrate on the most significant aspects of and important advances in
this field.
2 Applications of TiO 2 Nanomaterials in Photoelectrochemistry
Biosensing
In PEC biosensing, the photoactive material significantly influences the analytical performance. However, a well-known disadvantage of TiO 2 -based photoelectrochemistry is that the wide band gap of TiO 2 results in peak photoabsorption in
the ultraviolet (UV; λ ≤ 387 nm) [14, 21]. UV light decreases biomolecular activity,
which implies that the applicability of TiO 2 to PEC bioanalysis is limited [22]. Low
surface charge-transfer efficiency and high electron–hole pair recombination also
limit the sensitivities of TiO 2 -based biosensors. Therefore, attempts have been made
to identify new photoactive forms of TiO 2 that could be used to develop improved
biosensors. Countless works in the fields of materials and physical chemistry have
2
Reprinted from the journal
1 3
a target-recognition process when it is irradiated by light of a suitable wavelength.
PEC sensing analysis is more sensitive and has a lower background than traditional
electrochemical and optical detection techniques because it separates the excitation
source (light) from the output signal (photocurrent). Because of its low cost, high
sensitivity, very low background noise, short response time, ease of use, and ability
to be miniaturized, PEC biosensing has rapidly been applied in various contexts,
including for food detection, environmental monitoring, gene testing, and early clinical diagnosis [1–3].
Electrochemiluminescence (ECL)—electrogenerated chemiluminescence—can
be considered the reverse of PEC. ECL is the electrochemical process in which an
excited species is electrogenerated at an electrode surface and then allowed to relax
to a less excited state, resulting in the emission of light. As it is a combined electrochemical and spectroscopic technique, ECL permits both spectral and temporospatial resolution, which makes it a powerful tool for both sensing and imaging [4, 5].
The literature on ECL biosensing methods is extensive, which reflects their inherent advantages, including rapidity, simplicity, high sensitivity, low cost, and nearzero background signal. The integration of nanotechnology into ECL biosensors has
also significantly enhanced the sensitivity and diversity of ECL biosensors in recent
years [6].
TiO 2 nanomaterials are commonly used in PEC and ECL biosensors due to their
advantageous properties, such as strong light absorption, chemical and mechanical stability, good catalytic ability, high biocompatibility, and large specific surface
areas [7, 8]. There are three crystalline forms of TiO 2 : anatase, rutile, and brookite. The utilization of TiO 2 nanomorphologies such as nanosheets [9], nanopillars
[10], nanoarrays [11], nanoparticles [12], nanorods [13], nanowires [14], nanoneedles [15, 16], nanoflowers [17], nanocubes [18], and mesocrystals [19, 20] in many
advanced bioanalytical strategies is frequently reported.
In this mini review, we present recent advances in PEC and ECL biosensing
based on TiO 2 nanomaterials, exploring in detail the sensing strategies used and
response mechanisms involved. However, given the limited space available in a mini
review, we concentrate on the most significant aspects of and important advances in
this field.
2 Applications of TiO 2 Nanomaterials in Photoelectrochemistry
Biosensing
In PEC biosensing, the photoactive material significantly influences the analytical performance. However, a well-known disadvantage of TiO 2 -based photoelectrochemistry is that the wide band gap of TiO 2 results in peak photoabsorption in
the ultraviolet (UV; λ ≤ 387 nm) [14, 21]. UV light decreases biomolecular activity,
which implies that the applicability of TiO 2 to PEC bioanalysis is limited [22]. Low
surface charge-transfer efficiency and high electron–hole pair recombination also
limit the sensitivities of TiO 2 -based biosensors. Therefore, attempts have been made
to identify new photoactive forms of TiO 2 that could be used to develop improved
biosensors. Countless works in the fields of materials and physical chemistry have
2
Reprinted from the journal