A new study has obtained a range of hybrid photoactive materials with more stable and more rigid dyes that react differently when exposed to excitation light. Such hybrid materials, which combine components with various origins to achieve materials that differ from standard materials and can demonstrate new or improved properties, could lead to applications in areas including optics and biomedicine.

Researchers from the UPV/EHU, University of the Basque Country in Spain, whose study featured in Chemistry: A European Journal [Ortiz et al. Chem. Eur. J. (2017) DOI: 10.1002/chem.201701347], worked to develop and characterise the materials in numerous ways. For instance, hybrid materials were obtained by incorporating fluorescent dyes into channelled inorganic structures. This gives the dye protection, ensuring it is more stable against degradation and improves the term of devices incorporating them, as well as offering a more rigid system, possibly increasing the dye’s photophysical properties. The dyes are also ordered, providing a highly anisotropic response to the linearly polarized light so that they respond in a way that is dependent on the direction of the polarization of the incident light.

“Of great interest are those in which there is an artificial antenna effect with the ordering of the different kinds of dye and a unidirectional energy transfer”Rebeca Sola

Materials were also obtained with an extreme range of optical properties. As team leader Rebeca Sola said, “Of great interest are those in which there is an artificial antenna effect with the ordering of the different kinds of dye and a unidirectional energy transfer”. This provides particles with multi-coloured fluorescence that can pick up the energy from light at one end and then transfer it to the opposite end, an ability that could help integrate them into solar cells.

A solid material was shown to emit delayed fluorescence where, rather than the fluorescence of the system turning off once the excitation source is removed, it persists for a short time and is visible to the naked eye, offering potential uses in LED technology. In addition, materials capable of transforming incident laser light into light with double the amount of energy were demonstrated.

As well as materials allowing the incorporation of one dye into the inorganic structure, various dyes can be simultaneously encapsulated. For two dyes with complementary responses, the team obtained fluorescent particles that change color based on the light polarization, moving from a blue fluorescent emission to green, in a reversible and reproducible process. On incorporating a third, red-emission dye based on the correct proportions, a white-light emitting system was obtained.

These hybrid materials could find applications in biomedicine by using photosensitising substances suitable for photodynamic therapy, materials that combine organic and inorganic fragments to produce a kind of oxygen capable of killing some cells following excitation by light.