Luminescence Nanothermometry: Investigating Thermal Memory in UiO-66-NH2 Nanocrystals

Metal-organic frameworks (MOFs), a diverse and rapidly expanding class of crystalline materials, present many opportunities for various applications. Within this class, the amino-functionalized Zr-MOF, namely, UiO-66-NH2, stands out due to its distinctive chemical and physical properties. In this study, we report on the new unique property where UiO-66-NH2 nanocrystals exhibited enhanced fluorescence upon heating, which was persistently maintained postcooling. To unravel the mechanism, the changes in the fluorescence signal were monitored by steady-state fluorescence spectroscopy, lifetime measurements, and a fluorescence microscope, which revealed that upon heating, multiple mechanisms could be contributing to the observed enhancement; the MOFs can undergo disaggregation, resulting in a fluorescent enhancement of the colloidally stable MOF nanocrystals and/or surface-induced phenomena that result in further fluorescence enhancement. This observed temperature-dependent photophysical behavior has substantial applications. It not only provides pathways for innovations in thermally modulated photonic applications but also underscores the need for a better understanding of the interactions between MOF crystals and their environments.

Zero→Two-Dimensional Metal Nanostructures: An Overview on Methods of Preparation, Characterization, Properties, and Applications

Metal nanostructured materials, with many excellent and unique physical and mechanical properties compared to macroscopic bulk materials, have been widely used in the fields of electronics, bioimaging, sensing, photonics, biomimetic biology, information, and energy storage. It is worthy of noting that most of these applications require the use of nanostructured metals with specific controlled properties, which are significantly dependent on a series of physical parameters of its characteristic size, geometry, composition, and structure. Therefore, research on low-cost preparation of metal nanostructures and controlling of their characteristic sizes and geometric shapes are the keys to their development in different application fields. The preparation methods, physical and chemical properties, and application progress of metallic nanostructures are reviewed, and the methods for characterizing metal nanostructures are summarized. Finally, the future development of metallic nanostructure materials is explored.

Single-Crystalline Metal Oxide Nanostructures Synthesized by Plasma-Enhanced Thermal Oxidation

To unravel the influence of the temperature and plasma species on the growth of single-crystalline metal oxide nanostructures, zinc, iron, and copper foils were used as substrates for the study of nanostructure synthesis in the glow discharge of the mixture of oxygen and argon gases by a custom-made plasma-enhanced horizontal tube furnace deposition system. The morphology and microstructure of the resulting metal oxide nanomaterials were controlled by changing the reaction temperature from 300 to 600 °C. Experimentally, we confirmed that single-crystalline zinc oxide, copper oxide, and iron oxide nanostructures with tunable morphologies (including nanowires, nanobelts, etc.) can be successfully synthesized via such procedure. A plausible growth mechanism for the synthesis of metal oxide nanostructures under the plasma-based process is proposed and supported by the nanostructure growth modelling. The results of this work are generic, confirmed on three different types of materials, and can be applied for the synthesis of a broader range of metal oxide nanostructures.

Biocompatible Water Soluble Polyacrylic Acid Coated CdSe/Cu Quantum Dot Conjugates for Biomolecule Detection

Biocompatible polyacrylic acid functionalized CdSe/Cu quantum dot conjugates were synthesized to be used for biomolecules detection. The study results demonstrate the conjugation of the 2.5-3 nm QD with gram negative bacteria with a low detection limit of 28 cfu/ml. The photoluminescence (PL) intensity was correlated to bacterial count, cellular proteins and exopolysaccharides in the tested samples. Confocal Scanning Laser Microscopy (CSLM) images showed significant QD uptake within the cells, both cytoplasm and DNA were the predominant targeted biomolecules, higher fluorescent uptake was shown in gram negative bacteria than that observed for gram positive bacteria. Moreover, PL showed that there was a distinction between live and dead cells as well as gram negative and gram positive cells. Cell viability was not affected even after 6 days (100% viability) rendering it a non-toxic QD. The method is simple and is performed in a single step within approximately 10 min as compared to multi-step protocols for classical microbial count or fluorescent dye staining. All the above results indicate that the CdSe/Cu-PAA QDs are suitable for biomolecule detection, bio-labeling and bioimaging applications.

Synthesis of several novel coordination complexes: ion exchange, magnetic and photocatalytic studies

Eight different novel polymers by the reactions of H₂L and metal ions (Zn²⁺, Cu²⁺, Co²⁺) in the presence or absence of auxiliary ligands were constructed. The Zn²⁺ in complexes 1–3 could be partially exchanged with Cu²⁺ ions.

Methylresorcinarene: a reaction vessel to control the coordination geometry of copper(II) in pyridine N-oxide copper(II) complexes

Pyridine and 2-picolinic acid N-oxides form 2 : 2 and 2 : 1 ligand : metal (L : M) discrete L2M2 and polymeric complexes with CuCl2 and Cu(NO3)2, respectively, with copper(ii) salts. The N-oxides also form 1 : 1 host-guest complexes with methylresorcinarene. In combination, the three components form a unique 2 : 2 : 1 host-ligand-metal complex. The methylresorcinarene acts as a reaction vessel/protecting group to control the coordination of copper(ii) from cis-see-saw to trans-square planar, and from octahedral to square planar coordination geometry. These processes were studied in solution and in the solid state via(1)H NMR spectroscopy and single crystal X-ray diffraction.

Long-lived photoluminescence and high quantum yield of copper(ii) complexes with novel nanostructures

Four novel nano bipy-based copper(ii) complexes with high luminescence intensity, long-lived photoluminescence and quantum yield.

catena-Poly[[[aqua-(pyridine-2,6-dicarboxyl-ato N-oxide-κO,O)cobalt(II)]-μ-1,3-di-4-pyridylpropane-κN:N'] dihydrate]

In the title compound, {[Co(C₇H₃NO₅)(C₁₃H₁₄N₂)(H₂O)]·2H₂O}_n, the Co^II atom is coordinated by two O atoms from a pyridine-2,6-dicarboxyl­ate N-oxide ligand, two N atoms from two 1,3-di-4-pyridylpropane ligands and one water mol­ecule, and displays a distorted square-pyramidal coordination geometry. The 1,3-di-4-pyridylpropane ligands link the Co^II atoms into an infinite zigzag chain parallel to [010]. The chains are further linked through O—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional supra­molecular network.

Aqua-(picolinato N-oxide-κO,O)(pyridine-2,6-dicarboxyl-ato-κO,N,O')iron(III) monohydrate

In the title compound, [Fe(C₆H₄NO₃)(C₇H₃NO₄)(H₂O)]·H₂O, the Fe^III ion is coordinated by two O and one N atoms from a pyridine-2,6-dicarboxyl­ate ligand, by two O atoms from a picolinate N-oxide ligand and by one water O atom in a distorted octa­hedral geometry [Fe—O = 1.940 (3)–2.033 (3) Å and Fe—N = 2.057 (4) Å]. In the crystal structure, the coordinated and solvent water mol­ecules contribute to the formation of O—H⋯O hydrogen bonds, which link the mol­ecules into layers parallel to the ab plane.