KCs2Pb2(HCOO)2Cl5: A Lead Formate with Strong Second-Harmonic-Generation Response Obtained by an Anionic Substitution.

Nonlinear optical (NLO) materials are playing an increasingly vital role in laser science and technology. Herein, we report a new lead formate, KCs2Pb2(HCOO)2Cl5, successfully synthesized by using mild mix-solvothermal methods. By the anionic substitution of a [CH3COO] group with a [HCOO] group, the dipole moment of the distorted [PbCl4O2] polyhedron is increased. In contrast, polarization from the anionic group and the volume of the unit cell are reduced. Hence, KCs2Pb2(HCOO)2Cl5 possesses a strong second-harmonic-generation (SHG) response of 4.2 times that of KH2PO4 (KDP), a transparent window covering 0.43-1.87 µm, a large band gap of 3.52 eV, and moderate birefringence (0.11@1064 nm). Systematic theoretical calculations illustrate the origin of the linear and nonlinear optical properties of KCs2Pb2(HCOO)2Cl5. This research provides a viable strategy for the design and synthesis of new NLO crystals.

[Effect of Low-density Polyethylene Microplastics on Natural Attenuation of Oxygenated Polycyclic Aromatic Hydrocarbons in Soil].

The continuous accumulation of microplastics in agricultural soils may affect the natural attenuation of oxygen-containing polycyclic aromatic hydrocarbons (OPAHs). The effects of low-density polyethylene (LDPE) microplastics with the spiking proportion of 1 % and 0.01 % in soils on the natural attenuation of OPAHs were investigated via soil microcosm experiments. The relation between the response of bacterial communities and OPAHs dissipation was also explored. The initial content of OPAHs in the soil was 34.6 mg·kg-1. The dissipation of OPAHs in the soil on day 14 was inhibited by LDPE. The contents of OPAHs in LDPE groups were higher than that in the control by 0.9-1.6 mg·kg-1, and the inhibition degree increased with the proportion of LDPE. The contents of OPAHs were not significantly different among groups on day 28, indicating that the inhibitory effect of LDPE disappeared. LDPE did not change the composition of the dominant taxa in the OPAHs-contaminated soil community but influenced the relative abundances of some dominant taxa. LDPE increased the relative abundance of Proteobacteria and Actinobacteria at the phylum level and decreased that of Bacillus and increased those of Micromonospora, Sphingomonas, and Nitrospira (potential degrading bacteria of LDPE and endogenous substances) at the genus level, all four of which were the main genera dominating intergroup community differences. LDPE changed the α and ß diversity of bacterial communities, but the extents were not significant. LDPE affected the function of the bacterial community, reducing the total abundance of PAHs-degrading genes and some degrading enzymes, inhibiting the growth of PAHs-degrading bacteria and thus interfering with the natural decay of OPAHs.

New lead-iodide formates with a strong second-harmonic generation response and suitable birefringence obtained by the substitution strategy.

Nonlinear optical (NLO) crystals featuring a strong second-harmonic generation (SHG) response and suitable birefringence to achieve phase-matching are in urgent demand in industrial and commercial applications. Based on the substitution strategy, two new NLO lead-iodide formates, K2[PbI2(HCOO)2] and Rb2[PbI2(HCOO)2], have been successfully synthesized using a moderate mixed-solvothermal method. K2[PbI2(HCOO)2] and Rb2[PbI2(HCOO)2] exhibit strong phase-matching SHG responses of 8 and 6.8 × KDP, respectively, a suitable birefringence and transparent window covering most of the visible light and mid-IR region. Crystal structures and theoretical calculations unveil that the origins of the strong SHG response and suitable birefringence can be credibly attributed to the oriented arrangement of the highly distorted [PbI2O4] hexa-coordinated polyhedra, which are consistent in their local dipole moments, as well. This research provides a new strategy to explore high-performance NLO crystals.