OLEDs are attractive and distinctive light sources because of they are very thin, emit over an area and can be flexible. These features also make them very interesting for medical applications as compact, lightweight sources can enable ambulatory treatment. In photodynamic therapy (PDT), light in combination with a photosensitiser leads to the generation of reactive oxygen species that can kill nearby cells. We report the development of improved OLEDs for PDT. In particular, we show their use for antimicrobial PDT i.e. for killing bacteria, parasites and fungi in vitro.
A quantitative comparison of third-order nonlinear optical properties of colloidal gold nanoshells (NSs) and gold nanorods (NRs) in water solutions has been carried out using open- and closed-aperture Z-scan measurements, performed with femtosecond laser pulses over a broad range of wavelengths. Absorption saturation was found to be a dominant effect for all the studied nanoparticles; however, two-photon absorption (2PA) properties were also detected, and were clearly resolved especially at the shortest wavelengths used. The value of the merit factor σ2/M (2PA cross section scaled by the molecular weight) for the NRs (10×35 nm) at 530 nm is 7.5 (GM·mol/g), while for the NSs it is 1.9 (GM·mol/g) at the same wavelength.
A detailed comparison of third-order nonlinear optical properties of colloidal gold nanoshells (NSs) and gold nanorods (NRs) in water solutions has been carried out with the open- and closed-aperture Z-scan measurements, performed with femtosecond laser pulses over a broad range of wavelengths. Absorption saturation was found to be a dominant effect for all the studied nanoparticles, however two-photon absorption properties are also detected, especially at the shortest wavelengths studied. The value of the merit factor σ2/M (two-photon absorption cross section scaled by the molecular weight) for the NRs (10nm × 35 nm) at 530 nm is 7.5 (GM·mol/g), while for the NSs is 1.9 (GM·mol/g) at the same wavelength.
Single nanoparticle imaging is a powerful method to characterize nanoobjects and gain better understanding of their structural and optical properties. In our research we focus on plasmonic nanoparticles and particularly on anisotropic gold nanorods, which present interesting, polarization-dependent optical properties strictly correlated with their surface plasmon resonances. Here we discuss our results on two-photon excited luminescence imaging of a single gold nanorod. We analyze the dependence of the two-photon luminescence of a nanorod on the excitation wavelength, incident laser power and polarization, and contrast them with the data available in the literature.
Deoxyribonucleic acid (DNA) chains can be engineered for diverse nanophotonics applications by the insertion of molecular groups in different spatial configurations. DNA chains can be assembled into wire-like structures, origami structures, photonic crystal-like assemblies, liquid-crystal phases, and thin films. These structures can be made to serve as scaffolds for the organization of various organic molecules and nanoparticles. The properties of nanostructures can be modified by the use of DNA and DNA modified by the surfactants.
We synthesized a mixture composed of gold nanoparticles of various shapes using the wet chemistry method. The final
solution contained long nanorods, balls, disks and different spherical nanoparticles. To separate particles of individual
shapes from the reaction mixture, the solution was centrifuged in a glucose density gradient. A distribution of
nanoparticles based on their diameters was observed and each section was collected independently and each type of
nanoobjects was characterised separately. Finally, the difference in nanoparticle shapes depending on the presence of
Ag+ ions in the growth solution is reported and its influence on the separation is discussed.
Both nonlinear absorption and nonlinear refraction are effects that are potentially useful for a plethora of applications in
photonics, nanophotonics and biophotonics. Despite substantial attention given to these phenomena by researchers
studying the merits of disparate systems such as organic materials, hybrid materials, metal-containing molecules and
nanostructures, it is virtually impossible to compare the results obtained on different materials when varying parameters
of the light beams and different techniques are employed. We have attempted to address the problem by studying the
properties of various systems in a systematic way, within a wide range of wavelengths, and including the regions of onephoton,
two-photon and three-photon absorption.
The objects of our studies have been typical nonlinear chromophores, such as π-conjugated molecules, oligomers and
polymers, organometallics and coordination complexes containing transition metals, organometallic dendrimers, small
metal-containing clusters, and nanoparticles of various kinds, including semiconductor quantum dots, plasmonic
particles and rare-earth doped nanocrystals. We discuss herein procedures to quantify the nonlinear response of all of
these systems, by defining and comparing the merit factors relevant for various applications.
Azo-polymers have been the subject of a growing interest since the first demonstration of reversible birefringence and
dichroism effects induced optically at room temperature in such materials. It is well established that the mechanisms
involved are related to a molecular reorientation following photo induced trans-cis-trans isomerization of the
The interest for such materials has been strengthened with the more recent demonstration that the photo-isomerization
mechanisms can be employed to induce controlled topographic modifications. A simple example is the induction of a
sinusoidal modulation of the film surface by the irradiation with an interference pattern between two laser beams. Such a
simple step technique appears thus as a simple tool towards realisation of photonic devices.
However, if the realisation of gratings with periods in the visible wavelength scale is widely investigated, a strong
decrease of the patterning efficiency is observed in the case of periods below 400nm, limiting then the potential of the
In order to circumvent this problem we have developed a new azo-polymer presenting an absorption band shifted to the
Ultra Violet (UV) region of the spectrum. The possibility to induce gratings with periods down to 200nm with UV
irradiation is evidenced. Optical geometries of excitation have been implemented to optimise the modulation efficiencies.
As a potential application of the material investigated, the realisation of a polymer micro laser based on a distributed
feedback scheme is demonstrated.