Design and synthesis of pyrene-based probes and their fluorescent detection of Sb(III)

A series of pyrene-based fluorescent (FL) probes for Sb(III) were designed and synthesized. All of them exhibited luminescence by pyrene excimers in the mixture of DMSO and water and showed enhanced emission with the addition of Sb(III). By comparing their FL response to Sb(III), the effects of intramolecular hydrogen bond, inductive effect, and steric effect were investigated. Meanwhile, the FL enhancement factor of the best performing probe reached 10.28 and the detection limit was calculated to be 0.0535 mg/L, indicating that it might be used as a potential candidate for the treatment of Sb(III) in printing and dyeing wastewater.

Highly efficient recovery of Zn2+/Cu2+ from water by using hydrotalcite as crystal seeds

The efficient and waste-free recovery of heavy metals is critical for heavy metal wastewater treatment. In this work, we explored how heavy metals can be recovered as valuable chemicals in the presence of crystal seeds. Hydrotalcite (one kind of layered double hydroxides (LDHs)) was used as crystal seeds to recover Zn2+ in the presence of Al3+ from water (i.e., seed-Zn2+-Al3+ system), which was compared with the monometallic heterogeneous system (seed-Zn2+) and direct coprecipitation (Zn2+-Al3+) system. Our results demonstrated that the seed-Zn2+-Al3+ system possessed a recovery rate of 2.6-2.8 times and a recovery kinetic rate of 2.7-5.9 times higher than those of the other two systems. Differing from the latter two systems, hydrotalcite seeds could induce Zn2+ and Al3+ to form ZnAl-LDH in seed-Zn2+-Al3+. Interestingly, the ZnAl-LDH presents a compositional divalent/trivalent cation molar ratio of ca. 3, which is comparable with the value in the hydrotalcite. It was demonstrated that the hydrotalcite seeds could act as a template to significantly induce the formation of ZnAl-LDH complying with the seed's structure and compositional ratio. Similar induction effect of seeds as the Zn2+ system was further verified in Cu2+ systems. This work provides a novel strategy for efficient recovery of heavy metals with product selectivity.

Reversible sulfur dioxide capture by amino acids containing a single amino group at low sulfur dioxide concentrations

SO₂, an air pollutant, is harmful to human health and causes air pollution; therefore, numerous studies have focused on the development of SO₂ control technologies. Although limestone- and ammonia-based absorbents have been widely used in wet desulfurization, they are difficult to regenerate and do not enable the recycling of SO₂, which is a useful resource. Recently, amino acids have attracted attention as reversible SO₂ absorbents because they are eco-friendly and have excellent reactivity with SO₂, as well as high regeneration performance. Glycine, L-alanine, β-alanine, 4-aminobutyric acid, 5-aminovaleric acid, and 6-aminohexanoic acid were analyzed to investigate the relationship between SO₂ absorption and the amino acid molecular structure using the simulated actual flue gas (200 ppmv SO₂ + 13% CO₂ in N₂ balance). The SO₂ absorption of amino acids (with the molecular structure of glycine and alkyl chains of various lengths) improved as the alkyl chain length increased, possibly owing to a decrease in the inductive effect in the molecular structure of the amino acid. Furthermore, ¹³C-nuclear magnetic resonance spectroscopy was conducted to analyze the SO₂ absorption reaction mechanism (including the possible generation of irreversible species), and experiments involving a number of consecutive absorption-desorption cycles were used to confirm the reusability of the amino acids. The tested amino acids exhibited higher cyclic capacities compared to those of deep eutectic solvents and ionic liquids reported in the literature, thereby exhibiting excellent potential as SO₂ absorbents. Thus, this study can guide the future design and development of eco-friendly SO₂ absorbents.

Theoretical investigation of substituent effects on the relative stabilities and electronic structure of [BnXn]2- clusters

In this study, we provide a theoretical evaluation of relative stabilities and electronic structure for [B_nX_n]^2- clusters (n = 10, 12, 13, 14, 15, 16). Structural and electronic characteristics of [B_nX_n]^2- clusters are examined by comparison with the [B₁₂X₁₂]^2- counterparts with a focus on the substituent effects (X = H, F, Cl, Br, CN, BO, OH, NH₂) on the electronic structure, electron detachment energies, formation enthalpies, and charge distributions. For the electronic structure and electron detachment energies, substituent effects on boron clusters are shown to follow a very similar trend to the mesomeric and inductive effects (± M and ± I) of π-conjugated systems, and the most stable derivatives in terms of HOMO/LUMO and electron detachment energies are calculated for CN and BO substituents due to strong -M effects. In the case of formation enthalpies for larger boron clusters (n ≥ 13), the icosahedral barrier is shown to increase with the halogen and CN substitution, whereas it is possible to reduce the icosahedral barrier for the cases of X = OH and NH₂. It is shown that this reduction results from destabilizing the [B₁₂X₁₂]^2- cluster with electronic (+ M) and symmetry effects induced by OH and NH₂ ligands.

MXenes induced formation of Ni-MOF microbelts for high-performance supercapacitors

For the sake of developing new energy storage devices for satisfying the energy needs of the modern society, we herein report an innovative MXene-induced strategy to synthesize Ti₃C₂T_x MXenes/Ni based metal-organic framework composites (Ti₃C₂T_x/Ni-MOFs) for high-performance supercapacitors. The two-dimensional (2D) MXenes with oxygen-containing groups on the surface can be used as structure-directing agents to tune the Ni-MOFs into 2D microbelts. The presence of MXenes cannot only improve conductivity of the composite but also provide additional electric double layer capacitance and faradaic pseudocapacitance. The 2D Ni-MOF microbelts can offer rich activity sites for the faradaic redox reactions and shorten the ion transport path. Taking advantages of synergistic effects of Ni-MOF microbelts and Ti₃C₂T_x MXenes, the prepared Ti₃C₂T_x/Ni-MOFs electrode shows a good electrochemical performance with 1124 F g^-1 at the current density of 1 A g ^-1 and 62% rate capability at 20 A g ^-1. This work can offer a new insight to design 2D MOF belts as high-performance electrode materials for supercapacitors.

Escaping from poverty trap: a choice between government transfer payments and public services

Background

Anti-poverty has always been an important issue to be settled. What policies should be selected to help individuals escaping from the poverty trap: by directly offering transfer payments or indirectly providing public services? This paper is among the first to explore the effects of public anti-poverty programs system in China.

Methods

We Using unbalanced panel data of China Health and Nutrition Survey (CHNS) from 1989 to 2009, we demonstrate how the individual poverty status is determined through a four-staged simultaneous model. We choose the 3SLS (Three Staged Linear Squared) methodology to do the estimation.

Results

GTPs (Government Transfer Payments) don’t have positive effects on poverty reductions. The results demonstrate that GTPs increasing by 10% makes private transfer payments decrease by 3.9%. Meanwhile, GTPs increasing by 10% makes the household income decreased by 27.1%. However, public services (such as medical insurance, health services, hygiene protection etc.) have significantly positive impacts on poverty reduction. Public services share a part of living cost of the poor, and are conducive for people to gain higher household income.

Conclusions

GTPs given by governments are not effective in reducing the poverty, as a result of “crowd-out effect” and “inductive effect”. However, public services are suggested to be adopted by governments to help the poor out of the poverty trap.

A ligand-entry surface of the nuclear receptor superfamily consists of the helix H3 of the ligand-binding domain

We successfully simulated receptor-ligand complex holo-form formation using the human retinoid X receptor-α ligand-binding domain (LBD) and its natural ligand, 9-cis retinoic acid. The success of this simulation was strongly dependent on the findings for an initial structure between the apo-LBD and the ligand as well as the discovery of the driving forces underlying the ligand-trapping and subsequent ligand-induction processes. Here, we would like to propose the "helix H3 three-point initial-binding hypothesis," which was instrumental in simulating the nuclear receptor (NR) superfamily. Using this hypothesis, we also succeeded in simulating holo-form formation of the human retinoic acid receptor-γ LBD and its natural ligand, all-trans retinoic acid. It is hoped that this hypothesis will facilitate novel understanding of both the ligand-trapping mechanism and the simultaneous C-terminal folding process in NR LBDs, as well as provide a new approach to drug design using a structure-based perspective.

Gold-Catalyzed Oxidation of Propargylic Ethers with Internal C-C Triple Bonds: Impressive Regioselectivity Enabled by Inductive Effect

Inductive perturbations of C-C triple bonds are shown to dictate the regiochemistry of gold-catalyzed oxidation of internal C-C triple bonds in the cases of propargylic ethers, resulting in highly regioselective formation of β-alkoxy-α,β-unsaturated ketones (up to >50/1 selectivity) via α-oxo gold carbene intermediates. Ethers derived from primary propargylic alcohols can be reliably transformed in good yields, and various functional groups are tolerated. With substrates derived from secondary propargylic alcohols, the development of a new P,N-bidentate ligand enables the minimization of competing alkyl group migration to the gold carbene center over the desired hydride migration; the preferred migration of a phenyl group, however, results in efficient formation of a α-phenyl-β-alkoxy-α,β-unsaturated ketone. These results further advance the surrogacy of a propargyl moiety to synthetically versatile enone function with reliable and readily predictable regioselectivity.