Two-step resonance energy transfer between dyes in layered silicate films

Tailoring a hybrid three-component photoinitiating system for 3D printing

In the field of additive manufacturing DLP vat technologies are promising 3D printing techniques. The need of highly efficient photoiniating systems drives us to the development of photocyclic 3-component initiators. In order to improve the 3D printing sensitivity, we present in this paper the use of synthesized clay to tune up the photochemistry underlying the initiating radical production. Therefore, a three-component initiating system, based on a cationic dye, two coinitiators and with a clay filler suitable for DLP 3D printing of acrylate resins leading to high quality of parts and low printing time, is developed.

Spectroscopic Studies of the Interactions between a Cationic Cyanine Dye and a Synthetic Phyllosilicate: From Photophysics to Hybrid Materials

The interaction of the cationic organic dye Astrazon orange R (AO-R) with the synthetic phyllosilicate Laponite leads to very interesting hybrid materials. Indeed, the Laponite nanoparticles modify the photophysical properties of AO-R, inducing a stabilization of its excited emissive state by preventing ultrafast isomerization. The long-lived emissive clay-dye hybrid complex can be used to develop efficient photoinitiating systems, leading to organic-inorganic hybrid crosslinked polymer materials.

Absorption, fluorescence, and acid-base equilibria of rhodamines in micellar media of sodium dodecyl sulfate

Rhodamine dyes are widely used as molecular probes in different fields of science. The aim of this paper was to ascertain to what extent the structural peculiarities of the compounds influence their absorption, emission, and acid-base properties under unified conditions. The acid-base dissociation (HR(+)⇄R+H(+)) of a series of rhodamine dyes was studied in sodium n-dodecylsulfate micellar solutions. In this media, the form R exists as a zwitterion R(±). The indices of apparent ionization constants of fifteen rhodamine cations HR(+) with different substituents in the xanthene moiety vary within the range of pKa(app)=5.04 to 5.53. The distinct dependence of emission of rhodamines bound to micelles on pH of bulk water opens the possibility of using them as fluorescent interfacial acid-base indicators.

On the interaction of triarylmethane dye crystal violet with LAPONITE® clay: using mineral nanoparticles to control the dye photophysics

The combination of an organic dye with clays leads to very interesting hybrid materials with original properties.

Promotion of Förster resonance energy transfer in a saponite clay containing luminescent polyhedral oligomeric silsesquioxane and rhodamine dye

A new hybrid photostable saponite clay with embedded donor-acceptor dyes was prepared and characterized in this work. The saponite is intercalated with a luminescent polyhedral oligomeric silsesquioxane, which transfers the photoexcitation energy directly to an acceptor dye (rhodamine B). The obtained composite material was characterized by means of XRD, TEM microscopy, and UV/Vis and photoluminescence spectroscopy. A physicochemical study showed that the system behaved as an efficient Förster resonance energy transfer pair, owing to the very good spectral overlap of donor emission (λem =510-540 nm) and acceptor absorption in the λ=530-570 nm range. The hybrid material represents the first example of a photonic antenna based on a synthetic saponite clay and can be considered a step forward in the search for new, efficient, and stable materials suitable for light-harvesting applications.

Size-matching effect on inorganic nanosheets: control of distance, alignment, and orientation of molecular adsorption as a bottom-up methodology for nanomaterials

We have been investigating complexes composed of nanolayered materials with anionic charges such as clay nanosheets and dye molecules such as cationic porphyrins. It was found that the structure of dye assembly on the layered materials can be effectively controlled by the use of electrostatic host-guest interaction. The intermolecular distance, the molecular orientation angle, the segregation/integration behavior, and the immobilization strength of the dyes can be controlled in the clay-dye complexes. The mechanism to control these structural factors has been discussed and was established as a size-matching effect. Unique photochemical reactions such as energy transfer through the use of this methodology have been examined. Almost 100% efficiency of the energy-transfer reaction was achieved in the clay-porphyrin complexes as a typical example for an artificial light-harvesting system. Control of the molecular orientation angle is found to be useful in regulating the energy-transfer efficiency and in preparing photofunctional materials exhibiting solvatochromic behavior. Through our study, clay minerals turned out to serve as protein-like media to control the molecular position, modify the properties of the molecule, and provide a unique environment for chemical reactions.