Amplified luminescence in organo-curium nanocrystal hybrids

Ligand-Assisted Direct Lithography of Upconverting and Avalanching Nanoparticles for Nonlinear Photonics

Upconverting nanoparticles (UCNPs) exhibit unique nonlinear optical properties that can be harnessed in microscopy, sensing, and photonics. However, forming high-resolution nano- and micropatterns of UCNPs with large packing fractions is still challenging. Additionally, there is limited understanding of how nanoparticle patterning chemistries are affected by the particle size. Here, we explore direct patterning chemistries for 6-18 nm Tm3+-, Yb3+/Tm3+-, and Yb3+/Er3+-based UCNPs using ligands that form either new ionic linkages or covalent bonds between UCNPs under ultraviolet (UV), electron-beam (e-beam), and near-infrared (NIR) exposure. We study the effect of UCNP size on these patterning approaches and find that 6 nm UCNPs can be patterned with compact ionic-based ligands. In contrast, patterning larger UCNPs requires long-chain, cross-linkable ligands that provide sufficient interparticle spacing to prevent irreversible aggregation upon film casting. Compared to approaches that use a cross-linkable liquid monomer, our patterning method limits the cross-linking reaction to the ligands bound on UCNPs deposited as a thin film. This highly localized photo-/electron-initiated chemistry enables the fabrication of densely packed UCNP patterns with high resolutions (∼1 μm with UV and NIR exposure; <100 nm with e-beam). Our upconversion NIR lithography approach demonstrates the potential to use inexpensive continuous-wave lasers for high-resolution 2D and 3D lithography of colloidal materials. The deposited UCNP patterns retain their upconverting, avalanching, and photoswitching behaviors, which can be exploited in patterned optical devices for next-generation UCNP applications.

Combining the Best of Two Chelating Titans: A Hydroxypyridinone-Decorated Macrocyclic Ligand for Efficient and Concomitant Complexation and Sensitized Luminescence of f-Elements

An ideal chelator for f-elements features rapid kinetics of complexation, high thermodynamic stability, and slow kinetics of dissociation. Here we present the facile synthesis of a macrocyclic ligand bearing four 1-hydroxy-2-pyridinone units linked to a cyclen scaffold that rapidly forms thermodynamically stable complexes with lanthanides (Sm³⁺ , Eu³⁺ , Tb³⁺ , Dy³⁺ ) and a representative late actinide (Cm³⁺ ) in aqueous media and concurrently sensitizes them. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed an increase in the Ln/An-O bond lengths following the trend Cm>Eu>Tb and EXAFS data were compatible with time-resolved luminescence studies, which indicated one to two water molecules in the inner metal coordination sphere of Eu(III) and two water molecules for the Cm(III) complex. Spectrofluorimetric ligand competition titrations against DTPA confirmed the high thermodynamic stability of DOTHOPO complexes, with pM values between 19.9(1) and 21.9(2).

Transforming lanthanide and actinide chemistry with nanoparticles

Lanthanides and actinides are used in a wide variety of applications, from energy production to life sciences. To address toxicity issues due to the chemical, and often radiological, properties of these elements, methods to quantify and recover them from industrial waste are necessary. When used in biomedicine, lanthanides and actinides are incorporated in compounds that show promising therapeutic and/or bioimaging properties, but lack robust strategies to target cancer and other pathologies. Furthermore, current decorporation protocols to respond to accidental actinide exposure rely on intravenous injections of soluble chelating agents, which are inefficient for treatment of inhaled radionuclides trapped in lungs. In recent years, nanoparticles have emerged as powerful tools in both industry and clinical settings. Because some inorganic nanoparticles are sensitive to external stimuli, such as light and magnetic fields, they can be used as building blocks for sensitive bioassays and separation techniques. In addition, nanoparticles can be functionalized with multiple ligands and act as carriers for selective delivery of therapeutic and contrast agents. This review summarizes and discusses recent progress on the use of nanoparticles in lanthanide and actinide chemistry. We examine different types of nanoparticles based on composition, functionalization, and properties, and we critically analyze their performance in a comparative mode. Our focus is two-pronged, including the nanoparticles free of lanthanides and actinides that are used for the detection, separation, or decorporation of f-block elements, as well as the nanoparticles that enhance the inherent properties of lanthanides and actinides for therapeutics, imaging and catalysis.