Periodic Reporting for period 4 - BILUM (Novel applications based on organic biluminescence)
Okres sprawozdawczy: 2020-10-01 do 2021-10-31
In BILUM, organic small molecules are investigated that show simultaneous fluorescence & phosphorescence with high efficiency at room temperature. This turns these molecules into dual state, or as we call them, biluminescent emitters. The emission shows two characteristic emission band, split by the eneretic splitting between singlet (fluorescence) & triplet (phosphorescence) states. The fluorescence has typical decay times in the ns range, whereas the phosphorescence is a quantum mechanically forbidden transition, rendering it slow with ms decay times. It is the main objective to investigate this biluminescence in detail to be able to exploit these unique properties in novel applications. BILUM is structured in different research directions (RDs). In RD-A, the weakly emitting phosphorescence is the central focus. We want to understand the nature of this phosphorescence, its limitations & potential to be further increased and adjusted to possible applications. In RD-B, we investigate effects of high population densities in such biluminescent emitters. This is central, as the phosphorescent lifetimes with ms values will inherently lead to saturation effects and, thus, dictate a delicate interplay between fluorescence and phosphorescence. In RD-C, we explore biluminescence systems as sensing platforms. Here especially oxygen sensing is easily possible, as the phosphorescence is highly oxygen sensitive. With the addition of the second fluorescence channel, such biluminescence emitters intrinsically sport a reference signal. Finally in RD-D, we utilize all or knowledge from RD-A to RD-C to design and synthesize novel biluminescent emitters. Here, the specifications are determined by the joint insights of the project and the targeted applications. Conclusions: All main objectives of BILUM have been successfully addressed. We have developed a deep understanding of the basic working mechanism of biluminescence, have developed and learned to understand even new materials and material systems, have pursued new applications in form of different sensor concepts and programmable luminescent tags. The latter can be used as dosimetry systems to quantify UV radiation, which is very important in the current UV desinfection markets.
Within BILUM, we worked on all 4 RDs. Importantly, we have estabished various experimental methodologies to fully investigate these biluminescent systems spectroscopically. Here, time & spectrally resolved photoluminescence spectroscopy has been set up (RD-A/-B), a gas mixing station has been adjusted to carry out oxygen sensing experiments (RD-C), a photoluminescence quantum yield setup has been completed, and a glovebox and an integrated spin coater have been installed to allow for sample preparation in controlled protected environment (all RDs). All these setups & tools have been installed in new TUD facilities in cleanroom laboratories. The main achievements are:
1. A detailed understanding of the interplay between fluorescence & phosphorescence in thin film biluminescence samples. It is observed that the long-living nature of the phosphorescence leads to very high triplet state populations that give rise to saturation and bimolecular interactions.
2. The development of transparent programmable organic luminescent tags (PLTs). This is a new technology developed in BILUM that allows for non-contact writing and erasing of information in thin film samples comprising biluminescent emitters.
3. The development of new biluminescent emitters (through design and synthesis) that allow for excitation using blue light. This is a key advance compared to UV-absorbing materials as the use of widely available blue and white LEDs as excitation sources is now possible.
4. The demonstration & detailed explanation of dual state energy transfer from a biluminescent donor material to a fluorescent acceptor molecule. Here, for both donor states (singlet and triplet), Förster Resonant Energy Transfer (FRET) takes place. Interestingly, and shown for the first time, the transfers happen from exactly the same molecular species but are separated by more than eight orders of magnitude in lifetime.
5. The realization of the continuous wave operation of the PLTs, which is possible by using emitter materials with a very high phosphorescence contribution to the overall luminescence. Here, the imprinted information can be read out under illumination, which is much more accessible as the time-gated read-out of the first demonstration.
6. The realization of sub-second programming times for the PLTs.
7. The development of a numerical model to describe the oxygen diffusion in PLTs. This model has been tested with experimental results obtained from PLTs directly (luminescence imaging) and can now be used to predict other materials systems.
8. The development of a wavelength sensing device that is able to detect monochromatic radiation with sub-nanometer precision. Here, the central element of this sensing device is a biluminescence/fluorescence hybrid system that produces a wavelength-specific signal fingerprint in the time-domain that can be read out with a conventional photo detector.
The development of the PLTs open up various new research and development directions. We have transferred this concept to be used as UV-dosimetry system and are currently planning a spin-off company based on the underlying technology. For this, we have been able to secure IP for the core technology. Apart from the dosimetry application, the PLTs have been used in proof-of-concept food packaging that can be re-used in a collaboration with a product design student. For the wavelength sensing device, we have filed a patent application. All major research results have been presented at scientific conferences and published in peer-review journals. The PLTs have been promoted through a press release that has attracted worldwide attention both from academia and industry.
1. A detailed understanding of the interplay between fluorescence & phosphorescence in thin film biluminescence samples. It is observed that the long-living nature of the phosphorescence leads to very high triplet state populations that give rise to saturation and bimolecular interactions.
2. The development of transparent programmable organic luminescent tags (PLTs). This is a new technology developed in BILUM that allows for non-contact writing and erasing of information in thin film samples comprising biluminescent emitters.
3. The development of new biluminescent emitters (through design and synthesis) that allow for excitation using blue light. This is a key advance compared to UV-absorbing materials as the use of widely available blue and white LEDs as excitation sources is now possible.
4. The demonstration & detailed explanation of dual state energy transfer from a biluminescent donor material to a fluorescent acceptor molecule. Here, for both donor states (singlet and triplet), Förster Resonant Energy Transfer (FRET) takes place. Interestingly, and shown for the first time, the transfers happen from exactly the same molecular species but are separated by more than eight orders of magnitude in lifetime.
5. The realization of the continuous wave operation of the PLTs, which is possible by using emitter materials with a very high phosphorescence contribution to the overall luminescence. Here, the imprinted information can be read out under illumination, which is much more accessible as the time-gated read-out of the first demonstration.
6. The realization of sub-second programming times for the PLTs.
7. The development of a numerical model to describe the oxygen diffusion in PLTs. This model has been tested with experimental results obtained from PLTs directly (luminescence imaging) and can now be used to predict other materials systems.
8. The development of a wavelength sensing device that is able to detect monochromatic radiation with sub-nanometer precision. Here, the central element of this sensing device is a biluminescence/fluorescence hybrid system that produces a wavelength-specific signal fingerprint in the time-domain that can be read out with a conventional photo detector.
The development of the PLTs open up various new research and development directions. We have transferred this concept to be used as UV-dosimetry system and are currently planning a spin-off company based on the underlying technology. For this, we have been able to secure IP for the core technology. Apart from the dosimetry application, the PLTs have been used in proof-of-concept food packaging that can be re-used in a collaboration with a product design student. For the wavelength sensing device, we have filed a patent application. All major research results have been presented at scientific conferences and published in peer-review journals. The PLTs have been promoted through a press release that has attracted worldwide attention both from academia and industry.
It can be concluded that BILUM has pushed the bounderies of understanding beyond the state-of-the-art found at the project beginning in many areas.
- We have gathered a detailed understanding of the dynamic range of biluminescence emitters with their vastly different excited state lifetimes of singlet and triplet states. Knowing these details, it is easier to design applications and tailor new materials to meet certain application needs.
- We have designed more than 10 new organic compounds that show room temperature phosphorescence along with the conventional fluorescence.
- With our study on Förster Resonant Energy Transfer originating from emissive singlet AND triplet states, we have added to the overall understanding of energy transfer mechanisms in multichromophore systems.
- For room temperature phosphorescence (RTP), we have developed 3 specific application concepts that make use of the unique RTP properties having very persistent emission. Those are: programmable luminescent tags, UV dosimeters, wavelength sensors. All of which have not been suggested in literature beforehand.
- One finding that is not fully investigated and will keep us interested beyond BILUM is the observation of RTP of thin films immersed in aqaueous solutions. Typically one assumes that the water environment also contributes to very efficient RTP quenching. This is a surprising results that we will continue to study in the near future. It may open up the application of RTP systems to biological environments.
- We have gathered a detailed understanding of the dynamic range of biluminescence emitters with their vastly different excited state lifetimes of singlet and triplet states. Knowing these details, it is easier to design applications and tailor new materials to meet certain application needs.
- We have designed more than 10 new organic compounds that show room temperature phosphorescence along with the conventional fluorescence.
- With our study on Förster Resonant Energy Transfer originating from emissive singlet AND triplet states, we have added to the overall understanding of energy transfer mechanisms in multichromophore systems.
- For room temperature phosphorescence (RTP), we have developed 3 specific application concepts that make use of the unique RTP properties having very persistent emission. Those are: programmable luminescent tags, UV dosimeters, wavelength sensors. All of which have not been suggested in literature beforehand.
- One finding that is not fully investigated and will keep us interested beyond BILUM is the observation of RTP of thin films immersed in aqaueous solutions. Typically one assumes that the water environment also contributes to very efficient RTP quenching. This is a surprising results that we will continue to study in the near future. It may open up the application of RTP systems to biological environments.