Photon Energy Upconverting Nanopaper: A Bioinspired Oxygen Protection Strategy

Abstract

The development of solid materials which are able to upconvert optical radiation into photons of higher energy is attractive for many applications such as photocatalytic cells and photovoltaic devices. However, to fully exploit triplet-triplet annihilation photon energy upconversion (TTA-UC), oxygen protection is imperative because molecular oxygen is an ultimate quencher of the photon upconversion process. So far, reported solid TTA-UC materials have focused mainly on elastomeric matrices with low barrier properties because the TTA-UC efficiency generally drops significantly in glassy and semicrystalline matrices. To overcome this limit, for example, combine effective and sustainable annihilation upconversion with exhaustive oxygen protection of dyes, we prepare a sustainable solid-state-like material based on nanocellulose. Inspired by the structural buildup of leaves in Nature, we compartmentalize the dyes in the liquid core of nanocellulose-based capsules which are then further embedded in a cellulose nanofibers (NFC) matrix. Using pristine cellulose nanofibers, a sustainable and environmentally friendly functional nanomaterial with ultrahigh barrier properties is achieved. Also, an ensemble of sensitizers and emitter compounds are encapsulated, which allow harvesting of the energy of the whole deep-red sunlight region. The films demonstrate excellent lifetime in synthetic air (20.5/79.5, O2/N2)-even after 1 h operation, the intensity of the TTA-UC signal decreased only 7.8% for the film with 8.8 μm thick NFC coating. The lifetime can be further modulated by the thickness of the protective NFC coating. For comparison, the lifetime of TTA-UC in liquids exposed to air is on the level of seconds to minutes due to fast oxygen quenching.

Red Light Activation of Ru(II) Polypyridyl Prodrugs via Triplet-Triplet Annihilation Upconversion: Feasibility in Air and through Meat

“…Finally, this singlet excited state returns to the ground state by fluorescent emission of a high-energy photon, thereby realizing upconversion. TTA-UC has been demonstrated in various organic, inorganic, and/or supramolecular materials [15,[18][19][20][21][22], as well as in nano-or micro-sized particles [23][24][25]. For biological applications, i.e., for drug delivery and activation [26,27] or bio-imaging [13,[28][29][30][31][32][33], one of the main problems of TTA-UC is its sensitivity to molecular oxygen, which readily quenches the triplet state chromophores involved in the TTA-UC mechanism.…”

Reversible oxygen addition on a triplet sensitizer molecule: protection from excited state depopulation

“…The most common process which leads to the loss of triplet excited states population is related to the presence of molecular oxygen in corresponding samples. 16 However, these approaches either require a change of sample's architecture or affect photophysical and chemical properties of a triplet sensitizer. 7 An efficient protection against oxygen quenching is essential for applications which include triplet excited state formation.…”

Efficient Broadband Triplet–Triplet Annihilation‐Assisted Photon Upconversion at Subsolar Irradiance in Fully Organic Systems

“…As suggested by Kobayashi and Konami calculations and demonstrated by Svagan et al, this strategy allows tuning the Q -band position while keeping the B -band almost unchanged. [ 30,35 ] Figure 2 depicts the molecular structure and absorption spectra of the complete set of synthesized light-harvesters (see Experimental Section and Supporting Information). It includes a Pt(II)-meso -tetra(4-fl uorophenyl)tetrabenzoporphyrin (PtT-PTBPF) and three derivatives (Pt1N, Pt2N, Pt3N) obtained by progressive condensation of naphthalene on the macrocycle in order to continuously shift the absorption towards low energies.…”

“…This concept was proposed for the fi rst time in 2007 by Baluschev and co-workers, who achieved NIR-to-vis conversion by exploiting two different sensitizers simultaneously excited by two lasers or by concentrated solar light (1 W cm −2 ), and only recently the same group developed a broadband absorption system probably because of a lack of suitable dyes available on the market. [ 29,30 ] Here, we have taken this approach to the extreme by synthesizing a full set of sensitizers that were designed ad hoc, and in which each sensitizer is able to transfer the harvested energy to the same emitter. In this way, we obtained an optimized sTTA-UC system with a continuous and broad absorption, which allowed achieving a QY UC as large as 10% under 1 sun of broadband non-coherent excitation light.…”