Structural, optical, photocatalytic, and optoelectronic properties of Zn2SnO4 nanocrystals prepared by hydrothermal method.

Zn2SnO4 (ZTO) nanocrystals are extensively studied in various fields. However, size-dependent ZTO nanocrystals are still challenging to understand their structural, optical, photocatalytic, and optoelectronic properties. ZTO nanocrystals are synthesized by a facile hydrothermal reaction method. The structural properties of the synthesized ZTO nanocrystals are studied by x-ray diffraction and transmission electron microscope. The sizes of the ZTO nanocrystals are controlled by the pH values of the precursor and the molar ratios of the Zn:Sn in the starting materials. ZTO nanocrystals with the small size of 6 nm and large size of 270 nm are obtained by our method. The Eu3+ ions are doped into ZTO nanocrystals to probe size-dependent Eu doping sites, which shows significant potential applications in light emitting diode phosphors. Moreover, the photocatalytic activity of ZTO nanocrystals on rhodamine (RhB) decoloration are investigated, and the results show that 6 nm ZTO nanocrystals show better performance in the photocatalytic decoloration of RhB compared to 270 nm nanocrystals. Most importantly, we design and fabricate optoelectronic devices to detect IR light based on our nanocrystals and a self-prepared NIR cyanine dye. The device based on small sized ZTO nanocrystals exhibits better device performance under 808 nm IR light compared to that of the large sized ZTO nanocrystals. We believe this work represents ZTO size-dependent properties in term of structural, optical, photocatalytic, and optoelectronic properties as a multifunctional material.

Indolizine-Cyanine Dyes: Near Infrared Emissive Cyanine Dyes with Increased Stokes Shifts.

Molecular engineering strategies designed to red-shift cyanine dye absorptions and emissions further into the near-infrared (NIR) spectral region are explored. Through the use of a novel donor group, indolizine, with varying cyanine bridge lengths, dye absorptions and emissions, were shifted deeper into the NIR region than common indoline-cyanines. Stokes shifts resulting from intramolecular steric interactions of up to ∼60 nm in many cases were observed and explained computationally. Molecular brightnesses of up to 5800 deep into the NIR region were observed. Structure-property relationships are explored for the six indolizine-cyanine dyes with varying cyanine bridge length and indolizine substituents showing broad absorption and emission tunability. The dyes are characterized by crystallography, and the photophysical properties are probed by varying solvent for absorption and emission studies. Computational data show involvement of the entire indolizine π-system during light absorption, which suggests these systems can be tunable even further into the NIR region through select derivatizations.