Researchers in Spain have developed new hybrid photoactive materials that incorporate fluorescent organic dyes and respond differently depending on light stimuli, giving them potential for a number of applications in optics, solar-energy devices, and biomedicine.
A team at the UPV/EHU-University of the Basque Country led by Rebeca Sola, a researcher in the Department of Physical Chemistry at the university’s Faculty of Science and Technology, has developed a range of hybrid materials that not only are photo active, but also have unique photophysical properties, according to researchers.
Hybrid materials combine components of both organic and inorganic materials to give them optimal capabilities, depending on what researchers are aiming for. Sola and her team have been working with hybrid photoactive materials that can be used to provide new capabilities for optical and biomedical applications, they said.
In recent work, the team developed and thoroughly characterized a number of hybrid, photoactive materials that respond differently when exposed to excitation light. They achieved this by incorporating fluorescent dyes--routinely used in solution--into channeled inorganic structures. The materials responded in a unique way, first providing dye protection, which rendered them more stable against degradation and can potentially increase the lifetime of the devices that use them.
Channeled aluminophosphate with various encapsulated dyes emitting in the blue, green, and red regions of the spectrum, occluded separately (left) or simultaneously in the correct proportions to produce white light (right), under ultraviolet excitation light. The materials are among a number of new hybrid materials developed by researchers in Spain with applications in biomedicine and optics, among others. (Source: Rebeca Sola. UPV/EHU University of the Basque Country)
The materials also used the dyes to provide the system with rigidity, which has great potential to increase the photophysical properties of the organic hosts, Sola said.
“Highly fluorescent materials in which the dyes are found to be ordered were obtained, thus providing a highly anisotropic response to the linearly polarized light,” she explained, adding that it is “fairly straightforward” to synthesize the materials. "Crystalline structures in which the dye has already been occluded inside are obtained without any need to apply a diffusion process to insert the dye into the crystal,” Sola said.
Because of the range of optical properties the materials inherently have, they can be used to develop novel applications in the optical field, according to researchers.
"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," Sola said. This means that particles with multi-colored fluorescence can pick up the energy from light at one end and transfer it to the opposite end, which could potentially be integrated into solar cells to improve their performance, she said.
Researchers also developed a solid material that emits delayed fluorescence, persisting for tenths of a second after light-excitation occurs and with fluorescence visible to the naked eye, Sola said. "This kind of technology could be of interest in LED technologies," she explained.
Other materials the team created are capable of transforming incident laser light into light with double the amount of energy, while others can emit white light and ambient-temperature phosphorescence thanks to the addition of small organic molecules to certain frameworks of metal ions and organic compounds known as Metal Organic Frameworks, according to researchers.
Sola and her team published a paper detailing their work in Chemistry, a European Journal.
All in all, the materials not only have applications for the optical field, but also for biomedicine through the use of photosensitizing substances that are well suited for photodynamic therapy, Sola said. These are materials that combine organic and inorganic fragments to produce a kind of oxygen capable of killing certain cells following exposure to light.
Photodynamic therapy, for instance, is used in dermatology to treat a range of skin diseases and even for different types of cancer. Materials the team developed that not only generate this type of cytotoxic oxygen but also which are fluorescent can be used for this purpose, as well as for bio-imaging, Sola said.
"The phototoxic action of these compounds is being explored by means of experiments in in-vitro cell cultures, and although the results are promising, we are still in the early phases of the study," she added.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.