Lecture
Introducing light into (bio)chemical analysis – recent progress in photoelectrochemical detection schemes
- at -
- ICM Saal 3
Lecture description
Sh. Zhao1, G. Göbel3, M. Riedel3, L. Chen1, M. Eickhoff2, W. Parak1, F. Lisdat3
1 Department of Physics, Center for Hybrid Nanostructures (CHyN), University of Hamburg, Germany
2 Institute of Solid State Physics, University of Bremen, Bremen, Germany
3 Biosystems Technology, Technical University Wildau, D-15745 Wildau, Germany
The illumination of sensing surfaces by light can be used for different purposes. In photoelectrochemical approaches it is mainly applied to excite a material and ensure that charge carriers are generated. Upon polarisation of an electrode which is carrying this material a photocurrent can be obtained. Since this is also connected to redox reactions at the material surface the photocurrent becomes a measure for the concentration of certain donor or acceptor molecule (depending on the direction of the photocurrent). Different semiconductor materials have been investigated for this type of application resulting in significant progress in the field [1].
The illumination can however, also be used to excite surface plasmon states when metallic nanoparticles are fixed additionally. This has been used to generate a
photocurrent at wavelengths where the semiconductor itself cannot absorb light [2].
Another aspect of photoelectrochemical detections systems is the sensitivity of the detection and application in biology. Here different strategies of signal enhancement can be seen. We have been contributing in the development of multiple layers of semiconductor nanostructures such as quantum dots in order to boost the response signal. In another direction of research longer nanowires have been shown to be beneficial for an improved ratio between signal and noise [3].
More recently we have exploited the combination of two semiconductor materials for an improved charge carrier separation since recombination of charge carriers diminishes a portion of generated electrons and holes. Titan dioxide has here been used as a high band gap material and CdSe/ZnS quantum dots as the light sensitive component. A significant enhanced sensor signal could be obtained. Since the TiO2 has been deposited on top of the immobilised quantum dots an additional advantage could be demonstrated – such an electrode structure was well suitable for the study of living cells. The TiO2 layer prevents any toxic effect to the biological system which cannot be avoided when a quantum dot electrode is used.
As an alternative approach we have also studied the usage of gold nanoclusters as light-sensitive component. This avoids the usage of any toxic compound. Since the magnitude of photocurrent generation was rather moderate amplification by exploiting surface plasmon effects has been further combined here [5].
Finally, it should be mentioned that complete photoelectrochemical cells can be constructed which allow power supply only by light and a power generation which is dependent on a certain analyte concentration [6].
[1] M. Riedel, D. Schäfer, F. Lisdat, "Quantum Dot Architectures on Electrodes for Photoelectrochemical Analyte Detection", Biocatalysis and Nanotechnology, edited by Peter Grunwald, Pan Stanford Series on Biocatalysis (2017)
[2] S. Zhao, M. Riedel, J. Patarroyo, N. Bastús, V. Puntes, Y. Zhao, F, Lisdat, W. Parak, Nanoscale, (2022), 14, 12048
1 Department of Physics, Center for Hybrid Nanostructures (CHyN), University of Hamburg, Germany
2 Institute of Solid State Physics, University of Bremen, Bremen, Germany
3 Biosystems Technology, Technical University Wildau, D-15745 Wildau, Germany
The illumination of sensing surfaces by light can be used for different purposes. In photoelectrochemical approaches it is mainly applied to excite a material and ensure that charge carriers are generated. Upon polarisation of an electrode which is carrying this material a photocurrent can be obtained. Since this is also connected to redox reactions at the material surface the photocurrent becomes a measure for the concentration of certain donor or acceptor molecule (depending on the direction of the photocurrent). Different semiconductor materials have been investigated for this type of application resulting in significant progress in the field [1].
The illumination can however, also be used to excite surface plasmon states when metallic nanoparticles are fixed additionally. This has been used to generate a
photocurrent at wavelengths where the semiconductor itself cannot absorb light [2].
Another aspect of photoelectrochemical detections systems is the sensitivity of the detection and application in biology. Here different strategies of signal enhancement can be seen. We have been contributing in the development of multiple layers of semiconductor nanostructures such as quantum dots in order to boost the response signal. In another direction of research longer nanowires have been shown to be beneficial for an improved ratio between signal and noise [3].
More recently we have exploited the combination of two semiconductor materials for an improved charge carrier separation since recombination of charge carriers diminishes a portion of generated electrons and holes. Titan dioxide has here been used as a high band gap material and CdSe/ZnS quantum dots as the light sensitive component. A significant enhanced sensor signal could be obtained. Since the TiO2 has been deposited on top of the immobilised quantum dots an additional advantage could be demonstrated – such an electrode structure was well suitable for the study of living cells. The TiO2 layer prevents any toxic effect to the biological system which cannot be avoided when a quantum dot electrode is used.
As an alternative approach we have also studied the usage of gold nanoclusters as light-sensitive component. This avoids the usage of any toxic compound. Since the magnitude of photocurrent generation was rather moderate amplification by exploiting surface plasmon effects has been further combined here [5].
Finally, it should be mentioned that complete photoelectrochemical cells can be constructed which allow power supply only by light and a power generation which is dependent on a certain analyte concentration [6].
[1] M. Riedel, D. Schäfer, F. Lisdat, "Quantum Dot Architectures on Electrodes for Photoelectrochemical Analyte Detection", Biocatalysis and Nanotechnology, edited by Peter Grunwald, Pan Stanford Series on Biocatalysis (2017)
[2] S. Zhao, M. Riedel, J. Patarroyo, N. Bastús, V. Puntes, Y. Zhao, F, Lisdat, W. Parak, Nanoscale, (2022), 14, 12048
