Song Dang

A robust near infrared luminescent ytterbium metal-organic framework for sensing of small molecules

The first near-infrared luminescent ytterbium metal-organic framework has been realized for the highly selective and sensitive sensing of small molecules.

A layer-structured Eu-MOF as a highly selective fluorescent probe for Fe3+ detection through a cation-exchange approach

A new series of lanthanide metal–organic frameworks, LnL (Ln = La, Y, Eu, Tb, and Gd), were prepared under hydrothermal conditions. The five compounds are all isostructural as confirmed by the analyses of single crystal and powder X-ray diffractions. The compounds exhibit layer-like structures with the [H2NMe2]+ cations being located in the interlayer channels, which can be easily replaced by a number of metal ions. Most interestingly, compound EuL performs as a rare example of a highly selective and sensitive luminescence sensor for Fe3+ ions based on total quenching of the Eu-luminescence via cation-exchange. The possible sensing mechanism was further explored in detail. Remarkably, it is the first Eu-MOF luminescent material to exhibit an excellent ability for the detection of Fe3+ ions in a biological system.

Tunable emission based on lanthanide(III) metal-organic frameworks: an alternative approach to white light

A new family of lanthanide metal–organic frameworks, LnL (Ln = Y, La–Yb, except Pm), were synthesized under hydrothermal conditions based on a semi-rigid trivalent carboxylic acid. All LnMOFs are isostructural based upon the analyses of single crystal and powder X-ray diffractions. The optical properties of compounds LnL can be easily tuned by doping methods, allowing for the syntheses of the materials with enhanced visible emission properties. Considering the intense blue-emission of the Dy compounds, it is expected that white light can be achieved by doping Dy and other red-emission lanthanide ions, such as Eu3+ or Sm3+. For the first time, without involving any emission from organic ligands, white-light emission was successfully realized by codoping Dy/Eu or Dy/Sm into analogic Gd compounds.

Near-infrared emission from novel tris(8-hydroxyquinolinate)lanthanide(III) complexes-functionalized mesoporous SBA-15

A novel mesoporous material covalently bonded with 8-hydroxyquinoline (HQ) was synthesized (designated as Q-SBA-15). The 5-formyl-8-hydroxyquinoline grafted to (3-aminopropyl)triethoxysilane, that is, alkoxysilane modified 8-hydroxyquinoline (Q-Si), was used as one of the precursors for the preparation of the Q-SBA-15 material. On the basis of the other function of the Q-Si of coordinating to lanthanide (Ln) ions, for the first time, the LnQ 3 complexes (Ln = Er, Nd, Yb) have been covalently bonded to the SBA-15 materials. The derivative materials, denoted as LnQ 3-SBA-15, were characterized by field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption, and fluorescence spectra. Upon excitation at the ligands absorption bands, all of these materials show the characteristic near-infrared (NIR) luminescence of the corresponding lanthanide ions through the intramolecular energy transfer from the ligands to the lanthanide ions. The NIR luminescence of these mesoporous materials was compared with that of the corresponding pure LnQ 3 complexes and discussed in detail.

Syntheses and structures of a series of uranyl phosphonates and sulfonates: an insight into their correlations and discrepancies.

Six uranyl phosphonates and sulfonates have been hydrothermally synthesized, namely, (H2tib)[(UO2)3(PO3C6H5)4]·2H2O (UPhP-1), Zn(pi)2(UO2)(PO3C6H5)2 (UPhP-2), Zn(dib)(UO2)(PO3C6H5)2·2H2O (UPhP-3), (HTEA)[(UO2)(5-SP)] (USP-1), (Hdib)2[(UO2)2(OH)(O)(5-SP)] (USP-2), and Zn(phen)3(UO2)2(3-SP)2 (USP-3) (tib = 1,3,5-tri(1H-imidazol-1-yl)benzene, pi = 1-phenyl-1H-imidazole, dib = 1,4-di(1H-imidazol-1-yl)benzene, TEA = triethylamine, phen = 1,10-phenanthroline, 5-SP = 5-sulfoisophthalic acid, and 3-SP = 3-sulfoisophthalic acid). UPhP-1 has been determined to be a layered structure constructed by UO7 pentagonal bipyramids, UO6 octahedra, and phenylphosphonates. Protonated tib plays a role in balancing the negative charge and holding its structure together. UPhP-2 is made up of UO6 octahedra, ZnO2N2 tetrahedra and PO3C tetrahedra in phenylphosphonates, forming a 1D assembly, which is stabilized by chelate phen ligand. Further connection of such chainlike structure via dib yields a 2D layered architecture of UPhP-3. Although sulfonate group possesses similar tetrahedral structure as the phosphonate group, a unidentated coordination mode is only found in this work. UO7 pentagonal bipyramids are linked by 5-SP to form the layered assembly of USP-1. USP-2 also consists of the same sulfonate ligand, but features tetranulear uranyl clusters. Similarly, protonated TEA and dib molecules enable stabilization of their structures, respectively. Formed by dinuclear uranyl cluster and 3-SP ligand, USP-3 appears as a 1D arrangement, in which Zn(phen)3 acts as the counterion to compensate the negative charge. All of these compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations.

Near Infrared and Visible Luminescence from Xerogels Covalently Grafted with Lanthanide [Sm3+, Yb3+, Nd3+, Er3+, Pr3+, Ho3+] β-Diketonate Derivatives Using Visible Light Excitation

A series of ternary lanthanide β-diketonate derivatives covalently bonded to xerogels (named as Ln-DP-xerogel, Ln = Sm, Yb, Nd, Er, Pr, Ho) by doubly functionalized alkoxysilane (dbm-Si) was synthesized in situ via a sol-gel process. The properties of these xerogel materials were investigated by Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), diffuse reflectance (DR) spectroscopy, thermogravimetric analyses, and fluorescence spectroscopy. The data and analyses suggest that the lanthanide derivatives have been covalently grafted to the corresponding xerogels successfully. Of importance here is that, after excitation with visible light (400-410 nm), the xerogels all show characteristic visible (Sm(3+)) as well as near-infrared (NIR; Sm(3+), Yb(3+), Nd(3+), Er(3+), Pr(3+), Ho(3+)) luminescence of the corresponding Ln(3+) ions, which is attributed to the energy transfer from the ligands to the Ln(3+) ions via an antenna effect. Exciting with visible light is advantageous over UV excitation. Furthermore, to the best of our knowledge, it is the first observation of NIR luminescence with visible light excitation from xerogels covalently bonded with the Sm(3+), Pr(3+), and Ho(3+) derivatives. Compared to lanthanide complexes (Ln = Er, Nd, Yb) functionalized periodic mesoporous organosilica (PMO) materials that exhibit similar optical properties reported in our previous work, the Ln-DP-xerogel (Ln = Sm, Yb, Nd, Er, Pr, Ho) in this case offer advantages in terms of ease of synthesis and handling and potentially low cost for emerging technological applications. Development of near-infrared luminescence of the lanthanide materials with visible light excitation is of strong interest to emerging applications such as chemosensors, laser systems, and optical amplifiers.

Near-Infrared Luminescence from Visible-Light-Sensitized Hybrid Materials Covalently Linked with Tris(8-hydroxyquinolinate)-lanthanide (Er(III), Nd(III), and Yb(III)) Derivatives

A series of new near-infrared (NIR) luminescent lanthanide-quinolinate derivatives [Ln(Q-Si)(3)] and xerogels (named as LnQSi-Gel, Ln = Er, Nd, Yb) covalently linked with the Ln(Q-Si)(3) by using the 8-hydroxyquinoline-functionalized alkoxysilane (Q-Si) have been synthesized. The obtained xerogel materials LnQSi-Gel are rigid and show homogeneous by field-emission scanning electron microscopy (FE-SEM) images. The Fourier-transform infrared (FT-IR), fluorescence spectra of Ln(Q-Si)(3), and LnQSi-Gel were measured, and the corresponding luminescence decay analyses were recorded. Of importance here is that the excitation spectra of the Ln(Q-Si)(3) and LnQSi-Gel extend to the region of visible light (more than 500 nm). Upon ligand-mediated excitation with the visible light, the Ln(Q-Si)(3) and LnQSi-Gel show the characteristic NIR-luminescence of the corresponding lanthanide ions through the intramolecular energy transfer from the ligands to the lanthanide ions. The good luminescent performances enable these NIR-luminescent xerogel materials to have possible applications in medical diagnostics, laser systems, and optics, etc.

Entangled metal–organic frameworks modulated by N-donor ligands of different conformations

Based on the aromatic dicarboxylic acid and N-donor ligands with different conformations, four Zn(II) metal–organic frameworks, namely [Zn(mfda)(L1)] (1), [Zn2(mfda)2(L2)]·DMF·H2O (2), [Zn2(mfda)2(L3)(H2O)]·DMF (3) and [Zn2(mfda)2(L4)] (4) have been synthesized (mfda = 9,9- dimethylfluorene-2,7-dicarboxylate anion, L1 = 1,10-phenanthroline, L2 = 4,4′-bipyridine, L3 = 2,5-bis(4-pyridyl)-1,3,4-ocadiazole and L4 = 1,4-bis(imidazol-1-ylmethyl)benzene). Single-crystal X-ray diffraction has revealed that all compounds exhibit entangled structures. Compound 1 is composed of 1D zigzag chains that are entangled through the π–π stacking interactions to generate a three-fold interpenetrating diamond-like networks. 2 exhibits a two-fold interpenetrating (α-Po) net, which leaves 1D channels with high free volume. In 3, parallel mutual polythreadings of 2D layers are connected by hydrogen bonds into a self-penetrating framework with (44·610·7)(4·5·6)(46·52·616·73·9) topology. For 4, the interpenetrating 2D layers are connected into a self-interpenetrating net with (49·66) topology. The potential of N-donor ligands to produce interesting metal–organic frameworks is investigated. Luminescent studies show that 1–4 exhibit strong blue fluorescent emissions.

Near-infrared luminescent copolymerized hybrid materials built from tin nanoclusters and PMMA

Novel near-infrared (NIR) luminescent copolymerized hybrid materials were prepared by covalently grafting and physically doping Ln complexes (Ln = Er, Sm, Yb, and Nd) into a copolymer matrix built from nanobuilding blocks. The structures of the obtained hybrid materials were investigated by Fourier transform infrared (FTIR) spectra, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). In the photoluminescence studies, the hybrid materials showed characteristic NIR luminescence of corresponding Ln(3+) ions through intramolecular energy transfer from ligands to Ln(3+) ions. Transparent films of these materials can be easily prepared through spin-coating on indium tin oxide (ITO) glasses taking advantage of the matrix nature.

Flexible Diphosphonic Acids for the Isolation of Uranyl Hybrids with Heterometallic U-VI=O-Zn-II Cation-Cation Interactions

A family of uranyl diphosphonates have been hydrothermally synthesized using various flexible diphosphonic acids and Zn(UO2)(OAc)4·7H2O in the presence of bipy or phen. Single-crystal X-ray analyses indicate that these compounds represent the first examples of uranyl phosphonates with heterometallic U(VI)═O-Zn(II) cation-cation interactions.