Photon upconversion
Photon upconversion is a photochemical method in which low-energy photons are converted into high -energy photons in a supramolecular gel . This requires visible light and chromophoric donor and acceptor molecules. Physically, this process is an anti- Stokes shift . This new approach uses supramolecular, viscoelastic gels as nanoreactors for photochemical and photophysical reactions such as photoinduced electron transfer , photosensitized reactions or photoisomerizations .
As in bionics , cells, enzymes, micelles , vesicles or membrane capsules are imitated and used as micro- or nano-reactors.
Composition of the gel
Self-organizing supramolecular gels with chromophoric donor-acceptor systems guarantee photon upconversion even with weak light irradiation.
- Pt Pc (OBu) 8 with rubrics in DMF (see figure)
- Palladium (II) mesoporphyrin with 9,10-diphenylanthracene (DPA) in dimethylformamide (DMF) / dimethyl sulfoxide
- Platinum tetraphenylporphyrin with DPA in 1,3,2,4-bis (3,4-dimethylbenzyl) sorbitol
- Platinum octaethylporphrine (PtOEP) with DPA in N, N′-bis (octadecyl) -L-Boc-glutamine diimide
Wavelengths of the excitation light from the laser
445 nm, 532 nm, 635 nm, 730 nm.
Electron transfer mechanism
Mechanistically, there is a triplet-triplet annihilation of the energy states:
In the ground state S o, the donor molecule absorbs low-energy photons, gets into the singlet state S 1 , slips through intersystem crossing (ISC) to the T 1 energy state, after which there is triplet-triplet energy transfer from the donor to the acceptor. If two acceptor molecules come together, what is known as triplet-triplet annihilation (TTA) occurs and fluorescence occurs .
application
A possible application for photovoltaic systems is conceivable. They could also be used in the field of medical imaging procedures . The method can also be used for the chemical breakdown of chlorine hydrocarbons. For example, aryl halides can be reduced photochemically in this way.
literature
- Pengfei Duan, Nobuhiro Yanai, Hisanori Nagatomi, and Nobuo Kimizuka: Photon Upconversion in Supramolecular Gel Matrixes: Spontaneous Accumulation of Light-Harvesting Donor – Acceptor Arrays in Nanofibers and Acquired Air Stability , J. Am. Chem. Soc., 2015, 137 (5), pp 1887-1894, doi: 10.1021 / ja511061h .
- M. Häring, R. Perez-Ruiz, AJ von Wangelin, DD Diaz: Intragel Photoreduction of Aryl Halides by Green-to-Blue Upconversion under Aerobic Conditions Chem. Commun. 2015, 51, 16848–16851, doi: 10.1039 / c5cc06917c .
- Haase, M .; Schäfer, H .: Upconverting Nanoparticles . Angewandte Chemie International Edition., 2011, 50, 5808–5829. doi: 10.1002 / anie.201005159 .
- N. Yanai, N. Kimizuka: Recent emergence of photon upconversion based on triplet energy migration in molecular assemblies , Chem. Commun. 2016, 52, 5354-5370, doi: 10.1039 / C6CC00089D .
- R. Perez-Ruiz, DD Diaz, Soft Matter: Photophysical and photochemical processes in 3D self-assembled gels as confined microenvironments , 2015, 11, 5180-5187, doi: 10.1039 / C5SM00877H .
- R. Vadrucci., C.Weder, YC Simon, Mater. Horiz .: Organogels for low-power light upconversion , 2015, 2, 120–124, doi: 10.1039 / C4MH00168K .
- P. Duan, N. Yanai, H. Nagatomi, N. Kimizuka: Photon Upconversion in Supramolecular Gel Matrixes: Spontaneous Accumulation of Light-Harvesting Donor-Acceptor Arrays in Nanofibers and Acquired Air Stability , J. Am. Chem. Soc., 2015, 137, 1887-1894, doi: 10.1021 / ja511061h .
Individual evidence
- ↑ a b c News from Chemistry , 65, Nov. 2017, 1100–1105.
- ↑ Dav. K. Chatterjee, Muthu K. Gnanasammandhan, Yong Zang: Small Upconverting Fluorescent Nanoparticles for Biomedical Applications , 2010, Vol. 6, 24, 2781-2795 doi: 10.1002 / smll.201000418 .