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NIR Light Harvesting in Artificial Protein-Lipid-Chromophores Coassembled Molecular System

Periodic Reporting for period 1 - NIRLAMS (NIR Light Harvesting in Artificial Protein-Lipid-Chromophores Coassembled Molecular System)

Reporting period: 2020-01-01 to 2021-12-31

o What is the problem/issue being addressed?
This project had an aim of addressing the key issues of solid-state triplet-triplet annihilation based molecular photon upconversion like 1) aggregation of chromophores in the solid-state 2) oxygen quenching of the triplet state and 3) low upconversion quantum yield. Additionally, NIR/ red to Vis photon upconversion is more useful for fabricating solid-state TTA-UC systems with high-energy bandgap solar cells to utilize the full potential of solar photons. However low solubility of NIR to Vis dyes in synthetic polymers and quenching by molecular oxygen is a major issue. Therefore, through the project, we have addressed these issues by developing new photon upconversion bioplastics showing wideband (530–730 nm to blue) photon upconversion. Finally, we also developed a new recycling route for post-utility extraction of the chromophores from the bioplastics to avoid their leaching into the environment. Hence, overall we have been successful in developing new bio sustainable solid-state TTA-UC materials with high upconversion quantum yields in air.

o Why is it important for society?
Through a successful demonstration of functional fabrication and recycling of photon upconversion plastics developed in this project, we have given a new direction to design recyclable optical bioplastics materials in energy harvesting applications to strengthen the concept of circular bio economy and will boost the European bioplastic industry. It is important for society from both an economic and sustainability point of view. This is because the new photonic bioplastics that will be developed by this approach will be recyclable hence will prevent plastic waste and environmental degradation.

o What are the overall objectives?
The key objective of this project was to make highly efficient NIR/Red to Vis, aqueous and solid-state photon upconverting molecular systems operating via triplet-triplet annihilation based photon upconversion (TTA-UC) in the oxygenated environment using an innovative approach of protein-lipid-chromophores coassembly. This objective was achieved by employing three main tracks (WP1-WP3). Specific objectives and progress made towards their achievements are summarized below.

Specific Objectives:
1. Synthesis of metal porphycenes as new NIR sensitizers (WP1)
2. Synthesis of new Ionic acceptors/annihilators (WP1)
3. Formulation of protein-lipid-chromophores co-assembly for efficient triplet-triplet annihilation in solid-state in air (WP1-WP3)
Objective 1.
Progress and conclusions: We tried to synthesize 2,7,12,17-Tetrapropylporphycene with Pt, Pd, and Os a metal center. However, synthesis failed due to the polymerization of its precursor compound 2-methyl-4-propyl-3,5 dicarbethoxy pyrrole during synthesis.
As a contingency plan, we collaborators with Prof. Nobuo Kimizuka at Kyushu University, Japan, and Prof. Fabienne Dumoulin at Acibadem Mehmet Ali Aydinlar University Turkey. They provided us with a newly synthesized NIR sensitizer ((Os(m-peptpy)2(TFSI)2) and Zn-phthalocyanine). The (Os(m-peptpy)2(TFSI)2) was used for NIR to blue photon upconversion and Zn-phthalocyanin was used for NIR sensitized molecular photoswitching. The structure of sensitizers is shown in Fig. 1. The commercially available red and green sensitizer PdTPBP was successfully used to fabricate red to blue and green to blue photon upconversion

Objective 2.
Progress and conclusions: We synthesized four ionic annihilators, 1) Sodium-diphenylanthracenesulfonate (DPAS), 2) Disodium di-phenylanthracene bisulfonate (DPBS), 3) Disodium para-ter-phenyl biulfonate (p-ter-PBS) and 4) Sodium-TIPS-anthracene 2-sulfonate (TIPS-AnS) as shown in Figure 2. The DPAS and DPBS were used to prepare green to blue TTA-UC film and TIPS-AnS was used to form NIR/Red to blue TTA-UC films.

Objective 3.
Progress and conclusions: We investigated the formation of protein-surfactant-chromophores co-assembly with different sensitizer-annihilator pair and protein surfactant systems. The surfactants used were triton X-100 (TX), TX-100 reduced (TXr), Polyalkylene glycol and PEG-PPG-PEG, Pluronic® L-31 (Figure 3). First, we investigated the photophysical properties of chromophores in the native surfactants. The TX-100 performed best for G-TX-PtOEP-DPAS film ( green to blue UC). We replaced TX100 due to its toxicity with TX-100-reduced to form NIR / red to blue films. Other surfactants performed well but chromophores showed low fluorescence quantum yields. We tested proteins (gelatin, zein, and beta-Lactoglobullin, Figure 4) as matrices to fabricate surfactant-chromophore systems in the solid-state due to their oxygen barrier. Among them, gelatin forms optically transparent films. Zein and beta-Lactoglobullin form yellow and white translucent film hence were not used further.

The protein-surfactant-chromophores coassembled films were fabricated upon one-step drop-casting of the solution on a glass plate and air drying for 48 h (Figure 5). The NIR to blue and red to blue films are composed of G-TXr- Os(m-peptpy)2(TFSI)2-DPAS and G-TXr- PdTPBP-TIPS-AnS systems (Figure 6). The green to blue film showed a high UC quantum yield of 7.6 % whereas the red to blue film showed a UC quantum yield of 8.2 % in the air. The NIR to blue film has been prepared for proof-of-concept demonstration and its detailed analysis will be published later. Hence we could successfully fabricate new photon upconversion bioplastics films showing wide spectrum photon harvesting (530 nm to 730 nm).

o Publications in Scientific Journals
1) Bharmoria et al.J Mat. Chem. C, 2021, 2021,9, 11655-11661.
2) Bharmoria et al., Chem. Soc. Rev. 2020, 49, 6529-6554 (Highlighted at the Front Cover).
3) Fredrik et al. Bharmoria, J. Phys. Chem. B., 2021, 125, 6255–6263.
4) The Red/NIR to blue TTA-UC bioplastics film is submitted for publication in the journal "Adv. Funct. Mater."

The developed work was presented at many international Conferences and institutions for wide outreach.

Represented Images for the presentation of the overall theme of the project are provided as Scheme 1-3.
Progress beyond the state of the art:
We also developed bioplastic photoswitches wherein we expanded the back conversion wavelength of azobenzene derivative from 440 to 740 nm through triplet sensitization. For this, we dispersed an azobenzene derivative and triplet sensitizer, Zn-phthalocyanine in the G-TXr film. The G-TXr-AZO1-Zn-phthalocyanine film showed Z to E photoswitching upon 740 nm LED excitation which is different from its normal absorption in the blue region (440 nm). Through this work, we have addressed the issue of poor photoswitching of azobenzene in the solid-state (Figure 7).

Impacts: The developed technology would have wide socio-economic impacts. The developed photonic bioplastics present a new alternative to petroleum-derived plastics which have post-utility disposal issues due to their non-recyclability. Therefore, we have given a new direction to design recyclable optical bioplastics materials in energy harvesting applications to strengthen the concept of circular bioeconomy. It will impact society both from an economic and sustainability point of view. Because it will prevent plastic waste and if developed at an industrial scale it will boost the European bioplastics industry to develop new job opportunities.
Figure 8. Set of TTA-UC bioplastics integrated Cu2ZnGeS4-ZnxSn1-xO solar cell.
Figure 6. Absorption and emission spectra of a) G-TX-PtOEP-DPAS and b) G-TXr-PdTPBP-TIPS-AnS film.
Figure 9. The presentation of NIR induced photoswitching of azobenzene derivative
Scheme 2. Near Infra-red to Visible photon upconversion
Scheme 1. Jablonski diagram of triplet-triplet annihilation photon upconversion
Figure 2. Protein used to form bioplastics in the NIRLAMS project
Figure 3. NIR sensitizers attempted for synthesis or synthesized during NIRLAMS project
Figure 5. Schematic presentation of the preparation of G-TX-PtOEP-DPAS film.
Figure 7. Various TTA-UC films in daylight and upon exposure to LASERS of different wavelength (532
Figure 4. Acceptor/annihilators synthesized during NIRLAMS project
Figure 1. Non-ionic surfactant used to disperse chromophores in the protein films in NIRLA