Postsynthetic Modification of the Nonanuclear Node in a Zirconium Metal-Organic Framework for Photocatalytic Oxidation of Hydrocarbons.

Heterogeneous catalysis plays an indispensable role in chemical production and energy conversion. Incorporation of transition metals into metal oxides and zeolites is a common strategy to fine-tune the activity and selectivity of the resulting solid catalysts, as either the active center or promotor. Studying the underlying mechanism is however challenging. Decorating the metal-oxo clusters with transition metals in metal-organic frameworks (MOFs) via postsynthetic modification offers a rational approach to construct well-defined structural models for better understanding of the reaction mechanism. Therefore, it is important to expand the materials scope beyond the currently widely studied zirconium MOFs consisting of Zr6 nodes. In this work, we report the design and synthesis of a new (4,12)-connected Zr-MOF with ith topology that consists of rare Zr9 nodes. FeIII was further incorporated onto the Zr9 nodes of the framework, and the resulting MOF material exhibits significantly enhanced activity and selectivity toward the photocatalytic oxidation of toluene. This work demonstrates a delicate ligand design strategy to control the nuclearity of Zr-oxo clusters, which further dictates the number and binding sites of transition metals and the overall photocatalytic activity toward C-H activation. Our work paves the way for future exploration of the structure-activity study of catalysts using MOFs as the model system.

Effects of dietary sorghum dried distiller's grains with solubles on growth performance, diet nutrient digestibility, carcass characteristics and immunity in growing rabbits.

Sorghum dried distiller's grains with solubles (S-DDGS) are distillation extract residues from the ethanol fuel industry. In this experiment, two hundred 42-day-old rabbits were randomly allocated to five experimental diets containing 0 g/kg (control), 75, 150, 225 and 300 g/kg S-DDGS. The experiment lasted for 4 weeks. No difference was found in the average daily feed intake (ADFI; p > 0.05). With increasing sorghum inclusion, the average daily gain (ADG) was linearly (p < 0.001) and quadratically (p = 0.039) reduced, while, conversely, the feed conversion ratio (FCR) linearly (p < 0.001) increased. Increasing the amount of S-DDGS in the diet linearly decreased (p < 0.001) the apparent total tract digestibility (ATTD) of dry matter (DM), organic matter (OM), crude protein (CP) and ash. Carcass weight, carcass yield, heart and liver weights were linearly decreased by an increase in the amount of S-DDGS added to diets (p < 0.001), but no difference was observed between the 0, 75 and 150 g/kg S-DDGS groups (p > 0.05). Serum IL-6, IL-10 and SIgA linearly increased (p = 0.008) with increasing levels of S-DDGS in the diet. Rabbits fed 0, 75 and 150 g/kg of S-DDGS had similar IL-6 and IL-10 levels. Statistically significant differences in SIgA were observed between rabbits fed control diets and feed mixtures containing S-DDGS (p < 0.01). To conclude, S-DDGS can safely be added up to 75 g/kg, to the diet of rabbits. Increasing dietary S-DDGS inclusion may decrease the growth performance, nutrient digestibility and carcass traits, and activate immune responses.

Donor-Acceptor Fluorophores for Energy-Transfer-Mediated Photocatalysis.

Triplet-triplet energy transfer (EnT) is a fundamental activation pathway in photocatalysis. In this work, we report the mechanistic origins of the triplet excited state of carbazole-cyanobenzene donor-acceptor (D-A) fluorophores in EnT-based photocatalytic reactions and demonstrate the key factors that control the accessibility of the 3LE (locally excited triplet state) and 3CT (charge-transfer triplet state) via a combined photochemical and transient absorption spectroscopic study. We found that the energy order between 1CT (charge transfer singlet state) and 3LE dictates the accessibility of 3LE/3CT for EnT, which can be effectively engineered by varying solvent polarity and D-A character to depopulate 3LE and facilitate EnT from the chemically more tunable 3CT state for photosensitization. Following the above design principle, a new D-A fluorophore with strong D-A character and weak redox potential is identified, which exhibits high efficiency for Ni(II)-catalyzed cross-coupling of carboxylic acids and aryl halides with a wide substrate scope and high selectivity. Our results not only provide key fundamental insight on the EnT mechanism of D-A fluorophores but also establish its wide utility in EnT-mediated photocatalytic reactions.

"π-Hole-π" Interaction Promoted Photocatalytic Hydrodefluorination via Inner-Sphere Electron Transfer.

We describe a metal-free, photocatalytic hydrodefluorination (HDF) of polyfluoroarenes (FA) using pyrene-based photocatalysts (Py). The weak "π-hole-π" interaction between Py and FA promotes the electron transfer against unfavorable energetics (ΔGET up to 0.63 eV) and initiates the subsequent HDF. The steric hindrance of Py and FA largely dictates the HDF reaction rate, pointing to an inner-sphere electron transfer pathway. This work highlights the importance of the size and shape of the photocatalyst and the substrate in controlling the electron transfer mechanism and rates as well as the overall photocatalytic processes.

Ultrafast kinetic DNA hybridization assay based on the visualization of threshold turbidity.

We report herein the development of an ultrafast kinetic DNA hybridization assay system based on the visualization of threshold turbidity associated with the assembly of polystyrene nanospheres. Initial testing of our diagnostic protocol on a sequence associated with the anthrax lethal factor indicates that a visually identifiable, turbidity-definitive, and kinetic threshold state could be reached at a time as short as 1 min. The assay scheme allows for both target concentration quantification and differentiation of single base mismatches through registry of the threshold turbidity onset time. The positively charged environment on nanospheres not only contributes to expedited signal generation but also imparts cooperative DNA binding properties. The kinetic visual protocol complements conventionally used thermodynamic strategies and provides an entry point for the circumvention of assay issues associated with ill-defined thermodynamic end points.

Robust Carbazole-Based Rare-Earth MOFs: Tunable White-Light Emission for Temperature and DMF Sensing.

Rare-earth metal-organic frameworks (RE-MOFs) are an attractive platform to construct luminescent materials for practical applications in lighting, optoelectronics, and sensing. By adjusting the metal composition in mixed RE-MOFs, one can not only realize tunable emission but also construct ratiometric luminescent sensors. As such, it is highly desirable to prepare robust RE-MOFs that display efficient, multifunctional sensing capability. In this work, we designed and synthesized a series of RE-MOFs that exhibit both excellent thermal and chemical stability due to the incorporation of a bulky tert-butyl group on a new carbazole-based ligand. By rationally tuning the molar ratio of Eu3+/Tb3+/Y3+, a white-light-emitting MOF was developed as an excellent thermal sensor that exhibits a temperature-induced ratiometric luminescence response between 278 and 378 K. After removing the coordinated solvent molecules via thermal treatment, the desolvated MOF materials exhibit excellent turn-on or color change sensitivity to recognize dimethylformamide (DMF) molecules. Such high sensitivity is attributed to the DMF coordination that induces the framework structure change and shifts the ligand's excited-state energy level to facilitate the ligand-to-metal energy transfer process. Taking together, NPF-700-RE represents a new class of robust, tunable luminescent materials that have great potential in white-light emission and thermal- and DMF-sensing applications.

Medium chain triglycerides improve the growth performance, immune and antioxidant functions, and intestinal health of weaned rabbits.

The purpose is to study the effects of different doses of medium chain triglyceride (MCT) on growth performance, immune and oxidative functions, and intestinal health of weaned rabbits. A total of 600 weaned rabbits weighing about 993.26 g and at 35 d of age were randomly divided into five groups. The control group was fed a basal diet containing 2400 mg/kg soybean oil, and the experimental group was substituted with 600, 1200, 1800, and 2400 mg/kg MCT. The whole trial period lasted for 48 d. The results showed that treatment with 2400 mg/kg MCT significantly increased the weaning survival rate and crude fat digestibility (p < 0.05) and dramatically raised the levels of serum immunoglobulin (Ig)A, IgG, IgM, catalase, superoxide dismutase, and total antioxidant capability (p < 0.05). The villus height and crypt depth in 1800 mg/kg MCT group were observably enhanced (p < 0.05). The abundance of Bacteroidetes was significantly increased in 1800 and 2400 mg/kg MCT groups (p < 0.05). In conclusion, 1800 and 2400 mg/kg MCT substituting soybean oil in the diet of weaned rabbits can improve the growth performance and intestinal barrier function of weaned rabbits.

A study of the physicochemical properties of rabbit glycated myofibrillary protein with high solubility in low ionic strength medium.

To analyze the physicochemical properties of rabbit glycated myofibrillary protein (GMP) with different solubility ((15.10 ± 0.76)%, (35.03 ± 1.01)%, (55.06 ± 1.25)%, and (75.07 ± 1.86)%) in low ionic strength medium, the changes in SDS-PAGE, foaming properties, emulsifying properties, gelling properties, rheological properties, and thermal stability under different pH conditions were determined. The results indicated that GMP with (75.07 ± 1.86)% solubility had better foaming and emulsifying properties than GMP with (35.03 ± 1.01)% solubility at pH 6.0 and pH 7.5 did; however, GMP with (75.07 ± 1.86)% solubility had lower gel strength and showed more cracks in gel networks. Furthermore, the storage modulus (G') of GMP increased as the solubility increased within the range of (15.10 ± 0.76)% to (35.03 ± 1.01)%, but decreased after the solubility reached (55.06 ± 1.25)%. Results also suggested that the glycation process can improve the thermal stability of myofibrillary protein; GMP with (75.07 ± 1.86)% solubility had the highest denaturation temperature. In conclusion, the physicochemical properties of rabbit GMP were affected by changes in solubility in low ionic strength medium; rabbit GMP with high solubility was more resistant to pH changes than native myofibrillary protein.

Effect of Growth on Fatty Acid Composition of Total Intramuscular Lipid and Phospholipids in Ira Rabbits.

The changes in fatty acid composition of total intramuscular lipid and phospholipids were investigated in the longissimus dorsi, left-hind leg muscle, and abdominal muscle of male Ira rabbits. Changes were monitored at 35, 45, 60, 75, and 90 d. Analysis using gas chromatography identified 21 types of fatty acids. Results showed that the intramuscular lipid increased and the intramuscular phospholipids (total intramuscular lipid %) decreased in all muscles with increasing age (p<0.05). An abundant amount of unsaturated fatty acids, especially polyunsaturated fatty acids, was distributed in male Ira rabbits at different ages and muscles. Palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), and arachidonic acid (C20:4) were the major fatty acids, which account to the dynamic changes of the n-6/n-3 value in Ira rabbit meat.

One-temperature synthesis of doped and alloyed Zn-Cd-Se nanocrystals.

A one-temperature strategy for the synthesis of both doped and alloyed semiconductor nanocrystals has been developed. Importantly, an intriguing band edge luminescence has been observed at high temperatures for the doped Zn-Cd-Se system, which is attributable to the excited state reservoir role played by the Zn(II) doping center in the excitonic recombination process.