ABSTRACT
Planar π-conjugated groups, like CO3, NO3, and BO3 triangles, are ideal functional units for designing birefringent materials due to their large optical anisotropy and wide band gap. The key point for designing birefringent crystals is to select appropriate functional building blocks (FBBs) and the proper arrangement mode. It is well known that the substitution strategy has proven to be a promising and accessible approach. In this work, alkali metals were chosen to regulate and control two different π-conjugated groups, CO3 and NO3, to build new compounds with large birefringence. Subsequently, three new compounds, Na3K6(CO3)3(NO3)2X·6H2O (X = NO3, Cl, Br), were successfully synthesized using the hydrothermal method. The aliovalent substitution between the [NO3]- anionic group and halogen anions [Cl]-/[Br]- has been achieved in these compounds. Na3K6(CO3)3(NO3)2X·6H2O feature the well-coplanar CO3 and NO3 groups in their crystal structure. This coplanar arrangement mode may effectively enhance the anisotropic polarizability of Na3K6(CO3)3(NO3)2X·6H2O. And their experimental birefringence can reach 0.094-0.131 at 546 nm. Diffuse reflectance spectra demonstrate that these compounds exhibit short ultraviolet (UV) absorption edges of â¼235 nm. Meanwhile, Na3K6(CO3)3(NO3)2X·6H2O also have an easily grown capacity under facile conditions. This work not only reports three new potential UV birefringent crystals but also provides a strategy to make the π-conjugated MO3 group coplanar.
ABSTRACT
As a neurotoxic and corrosive gas pollutant, H2S is unhealthy for all creatures and limits the development of the industry. By first-principles calculation, the adsorption behaviors of H2S gas on the original graphdiyne (GDY), non-metallic atoms decorated GDY, and metal atoms decorated GDY were initially studied. The adsorption configuration, adsorption energy, and charge transfer between H2S and GDY were calculated in detail. The electron density and the partial density of states (PDOS) were also examined. The results show that there is only weak physical adsorption between the original GDY, non-metallic atoms decorated GDY, and H2S gas molecules, so GDY and non-metallic atoms decorated GDY cannot be directly used to adsorb H2S gas. The adsorption of H2S gas on GDY decorated with metal atoms (Cu, Ti, and V) was significantly enhanced, and the adsorption in this condition belongs to chemical adsorption. They can be used as H2S gas adsorbing materials. In addition, the dissociation of H2S on transition metal atoms decorated GDY was further investigated. The results show that H2S in one of the five configurations dissociates on V-decorated GDY directly. Cu- and Ti-decorated GDY can be used as substrates for the dissociation of H2S. The energy barriers in this process are 1.605 eV and 0.360 eV, respectively. It is hoped that the research results in this work can provide insights into the development of H2S gas adsorbing and dissociating materials based on transition metal atoms decorated GDY.
ABSTRACT
Lone pair cation-based novel coordination compounds Sn[(pdc)(H2O)] (Sn-I) and (H2bpy)[Bi(pdc)2(Hpdc)]·5H2O (Bi-I) (pdc = pyridine-2,6-dicarboxylate; bpy = 4,4'-bipyridine) were synthesized through mild hydrothermal reactions. While Sn-I crystallizing in the polar space group, Pca21, exhibits a helical chain structure consisting of SnO3N distorted seesaws, 2,6-pdc linkers, and water molecules, Bi-I crystallizing in the centrosymmetric (CS) space group, P1Ì , reveals a pseudo-3D network composed of BiO5N3 polyhedra, 2,6-pdc ligands, H2bpy2+ cations, and isolated H2O molecules. The lone cations Sn2+ and Bi3+ in the title compounds are in a highly deformed polyhedral environment. The single-crystal-to-single-crystal transformation from Sn-I to the anhydrous Sn[(pdc)] (Sn-II) with the polar noncentrosymmetric structure was successfully achieved upon heating crystals of Sn-I. UV-vis diffuse reflectance spectra indicate that the introduction of Sn2+ or Bi3+ red-shifts the adsorption edges upon coordination. Powder second-harmonic generation (SHG) measurements indicate that Sn-I and Sn-II are type-I phase-matchable and exhibit SHG intensity of ca. 15 and 35 times that of α-SiO2, respectively. Solid state photoluminescence (PL) measurements indicate that Bi-I is an excellent green emitting phosphor with the quantum efficiency up to 26% and outstanding decay lifetime of 1.82 ms at room temperature.
ABSTRACT
To compare the efficacy of homemade anal cushion suspension clamp combined with harmonic scalpel (ACS) and Milligan-Morgan hemorrhoidectomy combined with electric knife (MMH) in the treatment of stages III to IV hemorrhoids. We conducted a retrospective study of 99 patients with stages III to IV hemorrhoids hospitalized from January to December in 2013. Among them, 51 patients were treated with ACS, while 48 patients received MMH. Data from clinical recording and follow-up included operative time, intraoperative blood loss, hospitalization information, postoperative pain, and postoperative complications. Operative time, intraoperative blood loss and hospitalization time in ACS group were significantly less than those in MMH group (Pâ<â.05). Compared with MMH group, ACS group had a lower postoperative static pain score from days 1 to 14 (Pâ<â.01). The patients in ACS group exhibited less postoperative defecation pain scores from days 3 to 20 than those of MMH group (Pâ<â.05). The incidence of postoperative anal edema and delayed wound healing in ACS group was lower than that in MMH group (Pâ<â.05). Compared with MMH, our novel technique ACS was more effective and had fewer postoperative complications in the treatment of stages III to IV hemorrhoids.
