Preparation of Novel Biodegradable Polymer Slow-Release Fertilizers to Improve Nutrient Release Performance and Soil Phosphorus Availability.

Inspired by the gradual collapse of carbon chain and the gradual release of organic elements into the external environment during the degradation of biodegradable polymers, a novel biodegradable polymer slow-release fertilizer containing nutrient nitrogen and phosphorus (PSNP) was prepared in this study. PSNP contains phosphate fragment and urea formaldehyde (UF) fragment, which are prepared by solution condensation reaction. Under the optimal process, the nitrogen (N) and P2O5 contents of PSNP were 22% and 20%, respectively. The expected molecular structure of PSNP was confirmed by SEM, FTIR, XRD, and TG. PSNP can release N and phosphorus (P) nutrients slowly under the action of microorganisms, and the cumulative release rates of N and P in 1 month were only 34.23% and 36.91%, respectively. More importantly, through soil incubation experiment and leaching experiment, it was found that UF fragments released in the degradation process of PSNP can strongly complex soil high-valence metal ions, thus inhibiting the phosphorus nutrient released by degradation to be fixed in the soil and ultimately effectively increasing the soil available P content. Compared with ammonium dihydrogen phosphate (ADP), a small molecule phosphate fertilizer that is easily soluble, the available P content of PSNP in the 20-30 cm soil layer is almost twice that of ADP. Our study provides a simple copolymerization method to prepare PSNP with excellent slow-release N and P nutrients, which can promote the development of sustainable agriculture.

Integration of efficient microwave absorption and shielding in a multistage composite foam with progressive conductivity modular design.

Ultra-efficient electromagnetic interference (EMI) shielding composites with excellent microwave absorbing properties are the most desirable solution for eliminating microwave pollution. However, integrating absorbing and electromagnetic shielding materials is a difficult challenge because they have different design strategies. In this work, the compatibility of high absorption and shielding capability based on progressive conductivity modular design was realized. Reduced graphene oxide@ferroferric oxide/carbon nanotube/tetraneedle-like ZnO whisker@silver/waterborne polyurethane (rGO@Fe3O4/CNT/T-ZnO@Ag/WPU) multistage composite foams with aligned porous structures were fabricated, which exhibited an excellent average EMI SE > 92.3 dB and remarkable microwave absorption performance with reflection loss < -10 dB in the frequency range of 8.2-18.0 GHz. The average shielding effectiveness of reflection (SER) and reflectivity (R) are as low as 0.065 dB and 0.015, respectively. Besides, the correlations between the morphology and structure of the composite foam and the electromagnetic wave attenuation mechanism were established via electromagnetic simulation. Significantly, the integration of efficient absorbing and shielding materials was realized for the first time. Such composite foams with electromagnetic wave absorption and shielding characteristics are light weight and structurally designable with an adjustable shielding mechanism, and exhibit low filler consumption and high performance. They display promising applications in demanding electromagnetic environments. Our work provides a new strategy to design ultra-efficient EMI shielding materials with reliable absorption-dominated features.

Self-driven microstructural evolution of Au@Pd core-shell nanoparticles for greatly enhanced catalytic performance during methanol electrooxidation.

The lack of direct insight into the microstructural evolution of catalytic materials under electrochemical polarization has inhibited the development of heterogeneous catalysts. By investigating a typical Au@Pd core-shell nanostructure, the present study discloses the microstructural evolution of heterogeneous catalytic materials during the methanol electrooxidation reaction (MOR). The electrocatalytic activity of the as-prepared Au@Pd_core-shell nanoparticles continuously increased during the first 100 successive voltammetry cycles of the MOR. Microstructural characterization studies revealed that during the MOR, an Au/Pd mixed bimetallic shell was formed by the self-driven microstructural evolution of the Au@Pd_core-shell nanoparticles. Both the experimental and calculation results indicated that the Au/Pd mixed bimetallic shell reduced the binding strength of OH- and CO on the catalyst surface. The exposed Au atoms in the shell region also produced large-scale reactive ˙OH radicals that facilitated the oxidative removal of the adsorbed carbonaceous species from the adjacent Pd active sites.

Polydopamine-Modified Al2O3/Polyurethane Composites with Largely Improved Thermal and Mechanical Properties.

Alumina/polyurethane composites were prepared via in situ polymerization and used as thermal interface materials (TIMs). The surface of alumina particles was modified using polydopamine (PDA) and then evaluated via Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and Raman spectroscopy (Raman). Scanning electron microscope (SEM) images showed that PDA-Al2O3 has better dispersion in a polyurethane (PU) matrix than Al2O3. Compared with pure PU, the 30 wt% PDA-Al2O3/PU had 95% more Young's modulus, 128% more tensile strength, and 76% more elongation at break than the pure PU. Dynamic mechanical analysis (DMA) results showed that the storage modulus of the 30 wt% PDA-Al2O3/PU composite improved, and the glass transition temperature (Tg) shifted to higher temperatures. The thermal conductivity of the 30 wt% PDA-Al2O3/PU composite increased by 138%. Therefore, the results showed that the prepared PDA-coated alumina can simultaneously improve both the mechanical properties and thermal conductivity of PU.

Biodegradable Urea-Formaldehyde/PBS and Its Ternary Nanocomposite Prepared by a Novel and Scalable Reactive Extrusion Process for Slow-Release Applications in Agriculture.

Novel binary composite urea-formaldehyde/poly(butylene succinate) (UF/PBS) and its ternary nanocomposite UF/PBS/potassium dihydrogen phosphate (MKP) were prepared by a simple and scalable reactive extrusion approach using methylolurea (MU), PBS, and MKP as the raw materials. The results show that MUs react by melt polycondensation to form UFs with different polymerization degrees at the high temperature in the extruder, giving the two polymer components molecular segment-scale mixing in composites. Meanwhile, MKPs dissolved in the water generated by the melt polycondensation are perfectly confined to the nanometer scale during their precipitation process in ternary composites due to the hydrogen bonding interactions between them and UF and the "cage effect" of UF and PBS macromolecule chains. Both composites have excellent processability, mechanical properties, and slow-release performances. Compared with UF prepared by direct synthesis or reactive extrusion, N release speeds of the two composites are much lower in the early incubation stage but much higher in the subsequent stages; ternary composites can also impart MKP with excellent slow-release properties. This study can provide a good feasibility for large-scale applications of UF-based or PBS-based composites and nanocomposites used as slow-release fertilizers or other products in agriculture or horticulture.

Stable and active Pt colloid preparation by modified citrate reduction and a mechanism analysis of inorganic additives.

Ultra-small and monodispersed Pt nanoparticles (NPs) have been successfully synthesized in polymer electrolyte membrane fuel cells. The process normally involves the use of capping agents, organic species, templates, and substrates and is thus complex. Hence, obtaining Pt NPs with a clean surface is challenging. In this study, a method for preparing stable and highly dispersed Pt NPs with clean surfaces is proposed. The method involves the use of a modified Na3C6H5O7 reduction process assisted by NaNO3 stabilization. The specific complexations of NO2- ions possibly alter the reaction kinetics and lower the growth rate of Pt NPs by retarding the reduction reaction. The optimized Pt/carbon nanotube (CNT) catalysts exhibit high mass activity and moderate activity decay after 10,000 times of potential cycling compared with commercially available Pt/C catalysts. Then, membrane electrode assemblies based on the resultant catalysts are characterized. The cell performance of 744 mW cm-2 (maximum power density) is achieved after the optimized Pt/CNT catalysts are used in carbon black.

Novel Semi-IPN Nanocomposites with Functions of both Nutrient Slow-Release and Water Retention. 2. Effects on Soil Fertility and Tomato Quality.

So far, the effects of the semi-interpenetrating polymer network (semi-IPN) composites with functions of both nutrient slow-release and water retention on soil physicochemical properties, yield, and quality of crops have not been studied. In Part 1 of this paper ( Song, J.; Zhao, H.; Zhao, G.; Xiang, Y.; Liu, Y. J. Agric. Food Chem. 2019 , DOI: 10.1021/acs.jafc.9b00888 ), superabsorbent polymers SAPWS (grafting wheat straw (WS) to poly(acrylic-co-acrylamide), which is WS-g-P(AA-co-AM)) and SAPHEC (HEC (hydroxyethyl cellulose)-g-P(AA-co-AM)), and their semi-IPN nanocomposites SI-PSRF/SAPWS and SI-PSRF/SAPHEC (formed by chemical bonding of SAPWS or SAPHEC with PSRF (NPK-containing polymeric slow-release fertilizer)) were prepared, and their microstructures and degradation performances were systematically studied. In this study, effects of these two nanocomposites on soil physicochemical properties, crop yield, and quality as well as soil fertility, especially the relationships between these effects and the degradation performances of the materials themselves, were investigated by a pot experiment of the tomato. Results show that SI-PSRF/SAP nanocomposites can regulate the pH values of weak alkaline soils close to 7.0. The changes of soil pH values, in our study, are basically synchronized with the degradation rates of SI-PSRF/SAP, the higher the degradation rate of SI-PSRF/SAP, the lower the pH value of the alkaline soil treated. Compared with PSRF+SAP (the simple physically mixed system of PSRF and SAP) and PSRF, during the whole growth period of the tomato, SI-PSRF/SAP treatments have the lowest nitrogen release amounts, 4.74 g for SI-PSRF/SAPWS and 4.88 g for SI-PSRF/SAPHEC, the highest nitrogen contents of soils after day 40, and the highest nitrogen contents of plants on day 100, 1.16 and 1.68 g for SI-PSRF/SAPWS and 1.26 and 1.86 g for SI-PSRF/SAPHEC. While for PSRF+SAPWS, PSRF+SAPHEC, and PSRF, they are 5.16 g, 0.81 g, 0.63 g and 5.26 g, 0.87 g, 0.66 g and 5.17 g, 0.63 g, 0.52 g, respectively. There is a significant positive correlation between the material degradation rates and their nitrogen release amounts in this study, while SI-PSRF/SAP systems have the highest correlation coefficient, 0.950. In addition, compared to the control blank, the SI-PSRF/SAP system significantly increases tomato yield, 270.1% for SI-PSRF/SAPWS and 301.7% for SI-PSRF/SAPHEC. Compared with PSRF+SAP, the SI-PSRF/SAP system can make the soil treated become a high-quality soil by influencing the soil pH value, conductivity, cation exchange capacity, and the contents of nitrogen, phosphorus, organic carbon, and active organic carbon, which have significant impact on the soil quality. The chemical-bonded functional nanocomposites with a semi-IPN three-dimensional network structures formed by hydrogen-bonding interactions among functional groups of their components can more efficiently improve soil fertility, increase soil nutrient supply capacity, and promote plants growth and development as well as solve the environmental pollution caused by traditional fertilizers. The technology reported in this paper is simple and feasible for large-scale production of fertilizer with both water retention and nutrient slow-release, even nanofertilizer, which has great application potential.

Novel Semi-IPN Nanocomposites with Functions of both Nutrient Slow-Release and Water Retention. 1. Microscopic Structure, Water Absorbency, and Degradation Performance.

Few studies have been conducted on the use of general nanotechnology-based principles for providing nutrients to crops. Water and fertilizer are the most important inputs in determining crop yield and profit. In this paper, super-absorbent polymers SAPWS (grafting wheat straw (WS) to poly(acrylic-co-acrylamide), which is WS-g-P(AA-co-AM)) and SAPHEC (HEC (hydroxyethyl cellulose)-g-P(AA-co-AM)) and their semi-interpenetrating polymer network (semi-IPN) nanocomposites SI-PSRF/SAPWS and SI-PSRF/SAPHEC (formed by chemical bonding of SAPWS or SAPHEC with PSRF (NPK-containing polymeric slow-release fertilizer)) were prepared. Due to the differences between activity and number of functional groups in WS and HEC, the water absorption properties and degradation performances of SAPWS and SAPHEC and their chemically bonded function nanocomposites SI-PSRF/SAPWS and SI-PSRF/SAPHEC are different. The maximum water absorption ratios of SAPWS, SAPHEC, SI-PSRF/SAPWS, and SI-PSRF/SAPHEC can reach 200.00 g/g, 240.00 g/g, 119.91g/g, and 127.43 g/g, respectively. Effects of the structures of these four materials on their degradation performances were studied via a tomato pot experiment. The changes in microstructures of these materials during the degradation processes were characterized by TEM, SEM, FTIR, XRD, XPS, and other techniques. Results show that the degradation rate of the chemically bonded functional nanocomposites with a semi-IPN structure SI-PSRF/SAP system is higher than that of SAP+PSRF (the simple physically mixed system of PSRF and SAP). Due to the differences among the activities and quantities of functional groups in WS and HEC, the water absorption properties of SI-PSRF/SAPWS and SI-PSRF/SAPHEC are different, and there are different degradation rates for these two functional nanocomposites.

Granular, Slow-Release Fertilizer from Urea-formaldehyde, Ammonium Polyphosphate, and Amorphous Silica Gel: A New Strategy Using Cold Extrusion.

A new granular, slow-release fertilizer prepared by a cold-extrusion strategy (GSRFEx) based on urea-formaldehyde (UF), ammonium polyphosphate (APP), and amorphous silica gel (ASG) was presented. Characterizations showed that there were strong hydrogen-bond interactions and good compatibility among UF, APP, and ASG in GSRFEx. The mechanical properties as well as the slow-release properties of GSRFEx were greatly enhanced after the addition of APP and ASG to UF. Rape pot experiments indicated that GSRFEx could improve N-use efficiency dramatically and thereby facilitate the growth of rape. Importantly, as an economical, effective, and environment-friendly technology, cold extrusion has great potential to be applied in horticulture and agriculture. We hope that our work can offer an alternative method for the design of slow-release fertilizers with desirable properties.

Gradient Structure Design of Flexible Waterborne Polyurethane Conductive Films for Ultraefficient Electromagnetic Shielding with Low Reflection Characteristic.

Highly efficient electromagnetic shielding materials entailing strong electromagnetic wave absorption and low reflection have become an increasing requirement for next-generation communication technologies and high-power electronic instruments. In this study, a new strategy is employed to provide flexible waterborne polyurethane composite films with an ultra-efficient electromagnetic shielding effectiveness (EMI SE) and low reflection by constructing gradient shielding layers with a magnetic ferro/ferric oxide deposited on reduced graphene oxide (rGO@Fe3O4) and silver-coated tetraneedle-like ZnO whisker (T-ZnO/Ag) functional nanoparticles. Because of the differences in density between rGO@Fe3O4 and T-ZnO/Ag, a gradient structure is automatically formed during the film formation process. The gradient distribution of rGO@Fe3O4 over the whole thickness range forms an efficient electromagnetic wave absorption network that endows the film with a strong absorption ability on the top side, while a thin layer of high-density T-ZnO/Ag at the bottom constructs a highly conductive network that provides an excellent electromagnetic reflection ability for the film. This specific structure results in an "absorb-reflect-reabsorb" process when electromagnetic waves penetrate into the composite film, leading to an excellent EMI shielding performance with an extremely low reflection characteristic at a very low nanofiller content (0.8 vol % Fe3O4@rGO and 5.7 vol % T-ZnO/Ag): the EMI SE reaches 87.2 dB against the X band with a thickness of only 0.5 mm, while the shielding effectiveness of reflection (SER) is only 2.4 dB and the power coefficient of reflectivity ( R) is as low as 0.39. This result means that only 39% of the microwaves are reflected in the propagation process when 99.9999998% are attenuated, which is the lowest value among the reported references. This composite film with remarkable performance is suitable for application in portable and wearable smart electronics, and this method offers an effective strategy for absorption-dominated EMI shielding.

Interfacial modification of basalt fiber filling composites with graphene oxide and polydopamine for enhanced mechanical and tribological properties.

Due to the chemical inertness of the basalt fiber (BF) surface, the weaker interfacial bonding between BF and polymer matrices will seriously affect the further application of basalt fiber enhanced composites. In this study, a continuous and compact graphene oxide (GO) layer was grafted onto the surface of basalt fiber (BF) using biomimetic polydopamine (PDA) as a bridge to improve the mechanical and tribological properties of polyamide 6. The impact and flexural strength of the PA6 composites filled by the GO grafting BF (GO-PDA-BF/PA6) indicated that the introduction of GO has made a larger improvement in interface bonding performance between BF and PA6 matrix. The friction and wear tests showed the wear rate of the GO-PDA-BF/PA6 composite decreased by 51% compared with BF/PA6 composites and it also showed the best wear resistance and load-carrying capacity under various applied loads and sliding speeds, explained by the improved interface bonding between GO-PDA-BF and PA6 matrix and the anti-wear protective transfer film formed by GO in the worn surface. This study provided a considerable flexibility strategy of tailoring the interfacial compatibility between reinforcement and matrix for effectively improving the comprehensive performance of composites.

Layer-by-layer decoration of MOFs on electrospun nanofibers.

The design and fabrication of novel organic-inorganic nanocomposite membranes using metal-organic frameworks as building blocks have attracted numerous scientists. Here, HKUST-1 particles were decorated on crosslinked polymer nanofibers through a layer-by-layer method. The immersion sequence, the crosslinking and the number of the deposition cycles have a significant impact on the formation of the HKUST-1 decorated nanofibrous membranes. Moreover, it has been shown that such a membrane could be applied as a catalyst for visual detection of hydrogen peroxide.

Sandwich-like layer-by-layer assembly of gold nanoparticles with tunable SERS properties.

Sandwich-like layer-by-layer thin films consisting of polyelectrolytes and gold nanoparticles were utilized to construct surface-enhanced Raman scattering (SERS) substrates with tunable SERS properties. It is found that both the size of the nanoparticles in the layers and the interlayer distance significantly influence the SERS performance of the multilayered thin film. These simple, low-cost, easily processable and controllable SERS substrates have a promising future in the field of molecular sensing.

(E)-1-Phenyl-3-[4-(trifluoro-meth-yl)phen-yl]prop-2-en-1-one.

In the title compound, C(16)H(11)F(3)O, the dihedral angle between the two rings is 48.8 (2)°. The crystal packing exhibits no classical inter-molecular inter-actions between the mol-ecules.

Di-µ-aqua-bis-{diaqua-[µ-4-({4-[bis-(2-hy-droxy-eth-yl)amino]-6-chloro-1,3,5-triazin-2-yl}amino)-benzene-sulfonato]-sodium(I)}.

In the dinuclear title compound, [Na(2)(C(13)H(15)ClN(5)O(5)S)(2)(H(2)O)(6)](n), two Na(+) cations, disposed about a centre of inversion, are linked by two bridging water mol-ecules. The coordination geometry is based on an O(5) donor set defined by four water mol-ecules and a 4-amino-benzene-sulfonate O atom in a distorted trigonal-bipyramidal geometry. In the crystal, significant O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds lead to the formation of a three-dimensional architecture.

3-Nitro-2-phenyl-chroman.

In the title compound, C(15)H(13)NO(3), the dihedral angle between the two aromatic rings is 79.25 (16)°.

Diphenyl-methyl isothio-cyanate.

The asymmetric unit of the title compound, C(14)H(11)NS, contains two mol-ecules in which the dihedral angles between the phenyl rings are 77.23 (7) and 86.30 (7)°. No aromatic π-π stacking inter-actions are observed.

1-Bromo-2-[(E)-2-nitro-ethen-yl]benzene.

In the title compound, C(8)H(6)BrNO(2), the dihedral angle between the planes of the benzene ring and the nitro group is 22.99 (12)°. In the crystal, inversion dimers associated by pairs of short Br⋯O contacts [3.2319 (17) Å] occur.

Diphenyl chloro-thio-phospho-nate.

The complete mol-ecule of the title compound, C(12)H(10)ClO(2)PS, is generated by crystallographic mirror symmetry, with the P, S and Cl atoms lying on the mirror plane. The resulting PO(2)SCl tetra-hedron is significantly distorted [O-P-O = 96.79 (9)°]. The crystal packing exhibits no directional inter-actions.