Relationships between foliar δ¹³C and foliar K of C₃ plants on the Qinghai-Tibet Plateau, China.

<p>A) all samples, B) graminoids, C) forbs, D) shrubs, E) <i>Stipa</i> and F) <i>Kobresia</i>. Values for the linear regression (<i>y</i>) and significance (<i>P</i>) are shown for each relationship and the slope of the regression is plotted where it is significant. Solid line for significance at <i>P</i><0.05, dashed line for significance at <i>P</i><0.1. Sample points are color coded according to their location in three altitudinal ranges.</p

Relationships between foliar δ¹³C and foliar N of C₃ plants on the Qinghai-Tibet Plateau, China.

<p>A) all samples, B) graminoids, C) forbs, D) shrubs, E) <i>Stipa</i> and F) <i>Kobresia</i>. Values for the linear regression (<i>y</i>) and significance (<i>P</i>) are shown for each relationship and the slope of the regression is plotted where it is significant. Solid line for significance at <i>P</i><0.05, dashed line for significance at <i>P</i><0.1. Sample points are color coded according to their location in three altitudinal ranges.</p

Multiple regressions between foliar δ¹³C (<i>y</i>) and altitude (<i>a.s.l.</i>), foliar N, foliar P and foliar K for all samples, graminoids, forbs, shrubs, <i>Kobresia</i> and <i>Stipa</i>.

<p>The leaf samples were from 82 sites on the Qinghai-Tibet Plateau, China.</p><p>Numbers in brackets are the sample numbers for the groups. The regression model is <i>y</i> = a+b<i>x</i>₁+c<i>x</i>₂+d<i>x</i>₃+e<i>x</i>₄ where <i>y</i> is δ¹³C⋅(‰) and <i>x</i>₁, <i>x</i>₂, <i>x</i>₃ and <i>x</i>₄ are altitude, foliar N, foliar P and foliar K, respectively.</p>***<p>, <i>P</i><0.001; ^**, <i>P</i><0.01; ^*, <i>P</i><0.05; ns, not significant.</p

Correlations (<i>r</i>) between foliar elements and altitude of taxonomic and life-form groups of C₃ species sampled from 82 sites on the Qinghai-Tibet Plateau, China.

<p>∑_{K+ Ca+ Mg}, sum of the K, Ca and Mg concentration in leaves; C/N, the ratio of foliar C concentration to N concentration; C/P, the ratio of foliar C concentration to P concentration; N/P, the ratio of foliar N concentration to P concentration.</p>***<p>, <i>P</i><0.001; ^**, <i>P</i><0.01; ^*, <i>P</i><0.05; ns, not significant.</p

Correlations (<i>r</i>) of foliar δ¹³C with foliar mineral elements and foliar element ratios of leaf samples from 82 sites on the Qinghai-Tibet Plateau, China.

<p>∑_{K+ Ca+ Mg}, sum of the K, Ca and Mg concentrations in leaves. C/N, the ratio of foliar C concentration to N concentration; C/P, the ratio of foliar C concentration to P concentration; N/P, the ratio of foliar N concentration to P concentration.</p>***<p>, <i>P</i><0.001; ^**, <i>P</i><0.01; ^*, <i>P</i><0.05; ns, not significant.</p

Locations of the 82 sampling sites on the Qinghai-Tibetan Plateau, China.

<p>Locations of the 82 sampling sites on the Qinghai-Tibetan Plateau, China.</p

Tunable Emission and Selective Luminescence Sensing in a Series of Lanthanide Metal–Organic Frameworks with Uncoordinated Lewis Basic Triazolyl Sites

Four isostructural lanthanide metal–organic frameworks (Ln-MOFs) {[Ln­(L)_1.5(H₂O)]­·4H₂O}_<i>n</i> (<b>1-Ln</b>) (Ln = Sm, Eu, Gd, and Tb) have been successfully synthesized under solvothermal conditions with 2-(1<i>H</i>-1,2,4-triazol-1-yl) terephthalic acid (H₂L) and Ln­(NO₃)₃­·<i>n</i>H₂O (<i>n</i> = 0, 6). <b>1-Ln</b> shows a binodal (3,8)-connected three-dimensional framework that possesses a one-dimensional pore channel decorated with uncoordinated Lewis basic triazolyl sites. <b>1-Eu</b> and <b>1-Tb</b> exhibit bright red and green emissions with absolute quantum yields of 9.1% for <b>1-Eu</b> and 53.3% for <b>1-Tb</b>. The luminescence explorations demonstrated that <b>1-Tb</b> exhibits high quenching efficiency and low detection limit for sensing Fe³⁺ and nitrobenzene. Meanwhile, the fluorescence intensity of the quenched <b>1-Tb</b> samples was resumed after washing with ethanol, which shows highly selective and recyclable luminescence sensing for Fe³⁺ and nitrobenzene. Importantly, by doping different concentrations of Eu³⁺ and Tb³⁺ ions, a series of dichromatic doped <b>1-Eu</b>_{<b><i>x</i></b>}<b>Tb</b>_{<b>1‑<i>x</i></b>} MOFs were fabricated, showing an unusual fluent change of the emissions color from green, yellow, orange, orange-red, and red

Ln(III)-MOFs (Ln = Tb, Eu, Dy, and Sm) based on triazole carboxylic ligand with carboxylate and nitrogen donors with applications as chemical sensors and magnetic materials

<p>Using a triazole carboxylic ligand (H₂L = 4-(1<i>H</i>-1,2,4-triazol-1-yl) isophthalic acid), four water-stable lanthanide metal–organic frameworks (Ln(III)-MOFs) (<b>1-Ln</b>, Ln(III) = Tb, Eu, Dy, and Sm), [Ln(L)(HL)(H₂O)₂], where the deprotonated H₂L ligands have two different coordination modes: L²⁻ and HL⁻ [(a): η²μ₂χ², η²μ₁χ²; (b): η²μ₁χ²], have been synthesized by solvothermal reaction and characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analyses show that Ln(III)-MOFs are isostructural with 2D-layered structures with uncoordinated carboxylic and triazole groups. The luminescent properties of <b>1-Tb</b> in aqueous solution containing different cationic solutions and small organic solvents have been explored under ultraviolet irradiation at room temperature. The high quenching constant <i>K</i>_<i>SV</i> values and low detection limits indicate that <b>1-Tb</b> exhibits extremely high detection sensitivity and selectivity toward Fe³⁺ ions and nitrobenzene; <b>1-Tb</b> can keep its original network and be reused after the sensing experiments, which provide us with an optical material for detecting Fe³⁺ ions and nitrobenzene. Magnetic studies show that antiferromagnetic exchange interactions exist between Dy(III) ions in <b>1-Dy</b>.</p

New Luminescent Three-Dimensional Zn(II)/Cd(II)-Based Metal–Organic Frameworks Showing High H₂ Uptake and CO₂ Selectivity Capacity

Three new three-dimensional (3D) luminescent metal–organic frameworks (MOFs), namely, [Zn₂(L)₂]·2DMA·3H₂O (<b>1</b>), [Zn₂(L)₂]·H₂O (<b>2</b>), and [Cd₂(L)₂]·H₂O (<b>3</b>) [H₂L = 2-(imidazol-1-yl)­terephthalic acid], have been solvothermally synthesized by using d¹⁰ metal ions Zn­(II)/Cd­(II) and H₂L in different solvent systems, which have been well characterized by elemental analysis, Fourier transform infrared spectroscopy, powder X-ray diffraction, and thermogravimetric analysis. As influenced by the different solvents and metal ions, single-crystal X-ray diffraction shows that <b>1</b> is a three-dimensional (3D) microporous framework with one-dimensional (1D) pores (10.85 × 8.79 Ų) based on the [Zn₂(μ₂-COO)₄] secondary building units, and <b>2</b> and <b>3</b> are two 3D isostructural networks composed by 1D zigzag chains, which are further connected by L^2– ligands into dense packing structures. Topology analyses reveal that <b>1</b> can be simplified as a binodal (6,3)-connected <i><b>ant</b></i> topological net with a point symbol of (4⁴·6³·8³)­(4⁸·6²), and <b>2</b> and <b>3</b> show binodal (4,4)-connected nets with a point symbol of (4·6³·8²). Gas sorption behaviors of <b>1</b> for N₂, H₂, CH₄, and CO₂ have been studied in detail at different temperatures, indicating that the high H₂ uptake and high selectivity for CO₂ will make it as potential gas storage and separation materials. Moreover, the solid state luminescent properties of <b>1</b>–<b>3</b> have also been measured and studied at room temperature

A Pb²⁺-based coordination polymer with 5-(1H-tetrazol-5-yl)isophthalic acid ligand: structure and photoluminescence

<p>A coordination polymer, [Pb₂(OH)(tzia)]·2H₂O (<b>1</b>), has been prepared by solvothermal reaction of 5-(1H-tetrazol-5-yl)isophthalic acid (H₃tzia) and Pb(NO₃)₂. The polymer <b>1</b> is based on an unprecedented centrosymmetric tetranuclear [Pb₄(OH)₂(COO)₄(ttaz)₂] cluster linked by a multidentate tzia ligand, affording a 2-D 3,6-connected <b>kgd</b> layer. The adjacent layers are further jointed by Pb⋯O interactions to form a 3-D supramolecular framework with a rare (3,8)-connected <b>tfz-d; UO</b>_<b>3</b> topology. Photoluminescent properties of H₃tzia, <b>1</b>, and <b>1</b>-desolvated have been further investigated, and it was interesting to find that <b>1</b>-desolvated due to the removal of lattice water molecules reveals stronger photoluminescence than <b>1</b>.</p