We report here a luminescent metal-organic framework [Zn3(TDPAT)-(H2O)3] [TDPAT = 2,4,6-tris(3,5-dicarboxyl phenylamino)-1,3,5-triazine] exhibiting strong luminescence at room temperature,which can serve as the first case of a dual functional luminescent sensor for quantitatively detecting the concentration of nitrobenzene and
temperature.
We report here a luminescent metal–organic framework [Zn3(TDPAT)(H2O)3] [TDPAT = 2,4,6-tris(3,5-dicarboxyl phenylamino)-1,3,5-triazine] exhibiting strong luminescence at room temperature, which can serve as the first case of a dual functional luminescent sensor for quantitatively detecting the concentration of nitrobenzene and temperature.
Open and friendly: The smallest member of the rht-type metal–organic frameworks (MOFs, see picture) constructed by a hexacarboxylate ligand with a nitrogen-rich imino triazine backbone shows a significantly enhanced gas binding affinity relative to all other isoreticular rht-type MOFs. The high adsorption capacity and remarkable selectivity of CO2 are attributed to the high density of open metal and Lewis basic sites in the framework.
Both left-handed and right-handed helical chains of [(VO2)(HPO4)]∞, which are linked by [M(4,4′-bpy)2] to form three-dimensional framework structures (see picture), are present in the structures of two novel inorganic–organic hybrid materials, [M(4,4′-bpy)2(VO2)2(HPO4)4]. These were prepared from hydrothermal systems and characterized by single-crystal X-ray diffraction. M=Co or Ni; bpy=bipyridine.
Here, we report two three-dimensional metal–organic frameworks of formula [Co2(4-ptz)2(bpp)(N3)2]n (1) and [Co3(OH)2(bdt)2(bpp)2(H2O)2]n (2), which were synthesized by hydrothermal reaction from the respective tetrazole ligand (5-(4-pyridyl)tetrazole (4-H-ptz) for 1 and 5,5′-(1,4-phenylene)bis(1-H-tetrazole) (H2bdt) for 2), long and flexible pyridyl-containing ligand 1,3-bi(4-pyridyl)propane (bpp), NaN3, and CoCl2. Both 1 and 2 consist of well-isolated one-dimensional cobalt(II) alternating chains further linked by the bpp and/or the tetrazole ligand, while their chain structures are totally different. The chains of 1 are formed by Co2+ ions bridged by single μ-EE-N3 and triple (μ-EO-N3)(μ-tetrazole)2 alternately, whereas the Co2+ ions are bridged by μ3–OH to form Co3(OH)2 chains in compound 2. Magnetic measurements demonstrate that compound 1 contains an alternating antiferromagnetic (AF)/ferromagnetic (FM) ferrimagnetic chain, while compound 2 exhibits the coexistence of spin canting, slow magnetic dynamics, and finite-size effect, with alternating AF/AF/FM ferrimagnetic chains.
A family of fluoride-bridged lanthanide compounds, [DyIIIF(oda)(H2O)3] (1, oda = oxidiacetate) and [LnIII2F2(oda)2(H2O)2] (Ln = Tb(2) and Dy(3)), was synthesized and characterized. To investigate the effects of bridging ligands on magnetic behaviors, two hydroxyl-bridged complexes of formulas [LnIII2(OH)2(oda)2(H2O)4] (Ln = Tb(4) and Dy(5)) were also synthesized. Magnetic measurements show that the magnetic behaviors of the compounds are obviously distinct. Compounds 1, 2, and 3 show ferromagnetic interactions, while only antiferromagnetic interactions are observed in compounds 4 and 5. Among these compounds,1 and 3 show frequency-dependent ac-susceptibility indicative of slow magnetic relaxation. Because the structures of Dy2 cores are very similar in compounds 3 and 5, it may be inferred that the differences of bridging ligands are mainly responsible for the distinct magnetic exchange interactions and relaxation dynamics.
Lanthanide-doped core–shell upconversion nanocrystals (UCNCs) have tremendous potential for applications in many fields, especially in bio-imaging and medical therapy. As core–shell UCNCs are mostly synthesized in organic solvents, tedious organic–aqueous phase transfer processes are usually needed for their use in bio-applications. Herein, we demonstrate the first example of one-step synthesis of highly luminescent core–shell UCNCs in the “aqueous” phase under mild conditions using innocuous reagents. A microwave-assisted approach allowed for layer-by-layer epitaxial growth of a hydrophilic NaGdF4 shell on NaYF4:Yb, Er cores. During this process, surface defects of the nanocrystals could be gradually passivated by the homogeneous shell deposition, resulting in obvious enhancement in the overall upconversion emission efficiency. In addition, the up-down conversion dual-mode luminescent NaYF4:Yb, Er@NaGdF4:Ce, Ln (Eu, Tb, Sm, Dy) nanocrystals were also synthesized to further validate the successful formation of the core–shell structure. More significantly, based on their superior solubility and stability in water solution, high upconversion efficiency and Gd-doped predominant X-ray absorption, the as-prepared NaYF4:Yb, Er@NaGdF4 core–shell UCNCs exhibited high contrast in in vitro cell imaging and in vivo X-ray computed tomography (CT) imaging, demonstrating great potential as multiplexed luminescent biolabels and CT contrast agents.
Monodisperse water-soluble LaF3:Ln3+ nanocrystals (NCs) have been successfully fabricated viaa fast, facile and environmentally-friendly microwave-assisted modified polyol process with polyvinylpyrrolidone (PVP) as an amphiphilic surfactant. The obtained NCs can be well dispersed in hydrophilic solutions with small sizes in the range of 9–12 nm. The LaF3:Ln3+ NCs (Ln = Eu, Nd, Ce, Tb, Yb, Er, Yb, Ho and Yb, Tm) have the unique feature of up–down conversion from visible to NIR emission owing to the ladder-like arranged energy levels of Ln3+ and in particular, the high efficiency upconversion of the two-photon, obtained from excitation by a continuous 980 nm laser. This investigation focuses on both the up and down conversion fluorescence properties of water-soluble monodisperse crystalline LaF3:Ln3+ NCs in such a small size. Furthermore, the three-dimensional PDMS rod-like fluorescence displays and a silica surface modification by a core/shell structure on the obtained NCs can improve the biocompatibility, indicating potential applications in optical 3D devices and as bio-probes.
Monodisperse water-soluble hexagonal phase Ln3+-doped NaGdF4 upconverting nanocrystals (UCNCs) have been successfully fabricated by means of a fast, facile, and environmentally friendly microwave-assisted route with polyethylenimine as the surfactant. Fine-tuning of the UC emission from visible to near-IR and finally to white light has been achieved. Furthermore, studies of the magnetic resonance imaging as well as the magnetization (magnetization–magnetic field curves) and the targeted recognition properties of FA-coupled amine-functionalized NaGdF4@SiO2 UCNCs indicate that the obtained NaGdF4UCNCs can be potential candidates for dual-mode optical/magnetic bioapplications.
Water-dispersible Re3+ doped CeF3 colloidal nanocrystals with well controllable morphology and high crystallinity have been successfully synthesized through a solvothermal process. The TEM images illustrate that the Re3+ doped CeF3 nanocrystals are rectangular (or cubic) with a mean diameter of ~10 nm. The excellent dispersibility in some of the polar solvents including water is achieved by using polyethyleneimine as the capping agent. The amine groups of the polymer chains on one hand bind to the nanocrystal surface; on the other hand the free ones could link to functional materials including bio-molecules. The CeF3 nanocrystals doped with Tb3+ and Dy3+ions show the characteristic emission of Tb3+ 5D4–7FJ (J = 6–3, with 5D4–7F5 green emission at 542 nm as the strongest one) and Dy3+ 4F9/2–6H15/2 (blue-green color at 478 nm) and 4F9/2–6H13/2(yellow color at 571 nm) transitions, respectively. The energy transfer from Ce3+ to Tb3+ and Dy3+was also investigated in detail. In vitro studies of Re3+ doped CeF3 colloidal nanocrystals on HepG2 cells confirm their excellent biological compatibility. The obtained solid CeF3:Tb3+/PDMS nanocomposites are very stable and flexible and exhibit strong green photoluminescence upon UV excitation.
A facile solution-phase route for the preparation of AgInSe2 nanocrystals was developed by using silver nitrate, indium stearate, and oleylamine–selenium (OAm–Se) as precursors. The evolution process of the AgInSe2 nanocrystals is discussed in detail and different reaction conditions all have a great impact on the growth and morphology of the nanocrystals. Alloyed AgIn(S1−xSex)2nanocrystals with controlled composition across the entire range (0 ≤ x ≤ 1) was also successfully prepared by modulating the S/Se reactant mole ratio. X-ray diffraction (XRD), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to confirm that the alloyed AgIn(S1−xSex)2 nanocrystals are homogeneous. The UV-vis absorption spectra revealed that the band gap energies of the alloyed AgIn(S1−xSex)2 nanocrystals could be continuously tuned by increasing the Se content.
A new facile solution method for the synthesis of high quality lead selenide (PbSe) nanocrystals with controllable size and shape was developed. A Pb–stearate complex and oleylamine–selenium (OLA–Se) were used as new precursors to prepare monodispersed nanocrystals instead of the traditional lead oxide (PbO) and trioctylphosphine–selenium (TOPSe). Both of the lead and chalcogenide precursors used in this method are inexpensive and air-stable, which largely reduces the cost of the reaction and simplifies the synthetic process. Five different shapes including quasi-spherical, cubic, octahedral, cuboctahedral and star shaped monodispersed PbSe nanocrystals were obtained, and the particle size can be easily tuned from [similar]18 nm to [similar]50 nm by varying the amount of oleic acid (OA) while keeping the amount of oleylamine (OLA) fixed. Oleic acid based growth orientation and shape evolution mechanism in double stabilizer surfactants was investigated in detail. The etching of PbSe nanocrystals was also observed when they were dispersed in toluene containing excessive amine over time, the etching process of oleylamine occurred on particle surfaces, and a new framework composed of nanorods formed around the nanocrystals. An ITO–PbSe–Al device based on a film of PbSe nanocrystals was constructed. The dark steadystate I–V characteristics of the films before and after ligand exchange revealed a broad prospect for the use of PbSe nanocrystals in light detection and infrared solar cells.
Visible-light-responsive photonic structures have been prepared in alcohol solvents by using silica-modified PbS colloidal nanocrystal clusters (CNCs) as building blocks. Further modification of the PbS CNCs with a coating of silica allowed the dispersion of the particles into nonaqueous solutions. Repulsive electrostatic and solvation forces contribute to the self-assembly of the PbS@SiO2 spheres. The core–shell particles have optical properties similar to those of CNCs, and they can also be assembled into close-packing films through simple drop-casting on silicon substrates. Embedding droplets of such a PbS@SiO2 colloidal solution in a polymer matrix produced solid composite materials with visible-light-responsive optical properties with potential applications as sensors and optical switches.
Highly monodisperse PbS colloidal nanocrystal clusters with well controllable size and size distribution, high crystallinity and high water solubility have been successfully synthesized through a modified polyol process. Thiourea stock solution was rapidly injected into diethyene glycol solution containing lead precursor at an elevated temperature to produce PbS clusters.The high reaction temperature allows for control over size and size distribution and yields highly crystalline products.The superior water solubility is achieved by using poly(acrylic acid) as the capping agent. The caboxylate groups of which partially bind to the nanocrystal surface and partially extend into the surrounding water. The uncoordinated caboxylate groups also bring high density of charges to the surface of CNCs at the same time. Moreover, the CNCs exhibit visible or near-infrared absorption even though the overall sizes of the particles are larger than the excitation Bohr radius. This is due to the fact that the clusters are composed of primary nanocrystals and the whole cluster shows optical property similar to the tiny primary nanocrystals.
