Carbon footprint of farming practices in farmland ecosystems on the North and Northeast China plains.

Fast development of farming practices in China is projected to result in additional carbon emissions and thus affect farmland ecosystems' environmental performance. Based on 454 farm surveys on the North and Northeast China Plain, the carbon footprint (CF) of two farmland ecosystems (irrigated system for wheat and maize on the North China Plain and rainfed system for maize on the Northeast Plain) were assessed and emission reduction pathways explored by quantifying greenhouse gas emissions of agricultural inputs and farm practices during the entire crop growing seasons with an agricultural footprint model. The results demonstrated that the GHG emissions from wheat and maize rotation in the irrigated system were 7.63 t CO2 eq ha-1 and 3.17 t CO2 eq ha-1 for single season maize in the rainfed system. While energy consumption accounted for 12.5%-21.3% of the carbon footprint in both systems, the group assessment found that the largest difference in GHG emissions between the high and low emission groups came from mechanical energy consumption. Approximately 50.6% and 39.2% of the mechanical carbon footprint of wheat and maize, respectively, were caused by irrigation practices in the irrigated system. Regarding the rainfed system, where 46.6% of mechanical carbon emissions were generated by maize tillage operations. In addition, scenario analysis indicated that the mechanical carbon footprint could be reduced to 56 kg CO2 eq t-1 for NCP-wheat and 26 kg CO2 eq t-1 for NCP-maize, respectively, by optimizing yields and irrigation practices in irrigated systems and that the mechanical carbon footprint of NEP-maize could be reduced to 25 kg CO2 eq t-1 by optimizing yields and tillage practices in rainfed systems. Therefore, improvement in mechanization in irrigation and tillage practices can contribute to reduce GHG emissions in China. Water-saving irrigation technology is recommended in irrigated area and conservation tillage is recommended in rainfed agricultural area to reduce carbon footprints.

Template-Free Synthesis of Phosphorus-Doped g-C3 N4 Micro-Tubes with Hierarchical Core-Shell Structure for High-Efficient Visible Light Responsive Catalysis.

This work reports a new form of tubular g-C3 N4 that is featured with a hierarchical core-shell structure introduced with phosphorous elements and nitrogen vacancies. The core is self-arranged with randomly stacked g-C3 N4 ultra-thin nanosheets along the axial direction. This unique structure significantly benefits electron/hole separation and visible-light harvesting. A superior performance for the photodegradation of rhodamine B and tetracycline hydrochloride is demonstrated under low intensity visible light. This photocatalyst also exhibits an excellent hydrogen evolution rate (3631 µmol h-1 g-1 ) under visible light. Realizing this structure just requires the introduction of phytic acid into the solution of melamine and urea during hydrothermal treatment. In this complex system, phytic acid plays as the electron donor to stabilize melamine/cyanuric acid precursor via coordination interaction. Calcination at 550 °C directly renders the transformation of precursor into such hierarchical structure. This process is facile and shows the strong potential toward mass production for real applications.

Adsorbed p-Aminothiophenol Molecules on Platinum Nanoparticles Improve Electrocatalytic Hydrogen Evolution.

Electrocatalytic hydrogen evolution is an important approach to produce clean energy, and many electrocatalysts (e.g., platinum) are developed for hydrogen production. However, the electrocatalytic efficiency of commonly used metal catalysts needs to be improved to compensate their high cost. Herein, the electrocatalytic efficiency of platinum nanoparticles (PtNPs) in hydrogen evolution is largely improved via simple surface adsorption of sub-monolayer p-aminothiophenol (PATP) molecules. The overpotential goes down to 86.1 mV, which is 50.2 mV lower than that on naked PtNPs. This catalytic activity is even better than that of 20 wt.% Pt/C, despite the much smaller active surface area of PATP-adsorbed PtNPs than Pt/C. It is theoretically and experimentally confirmed that the improved electrocatalytic activity in hydrogen evolution can be attributed to the change in electronic structure of PtNPs induced by surface adsorption of PATP molecules. More importantly, this strategy can also be used to improve the electrocatalytic activity of palladium, gold, and silver nanoparticles. Therefore, this work provides a simple, convenient, and versatile method for improving the electrocatalytic activity of metal nanocatalysts. This surface adsorption strategy may also be used for improving the efficiency of many other nanocatalysts in many reactions.

Realizing ultra-stable Ti3C2-MXene in aqueous solution via surface grafting with ionomers.

MXenes are the first class of 2D materials with the combination of metallic conductivity and hydrophilicity. However, degradation forms a key drawback limiting their long-term applications. This work for the first time demonstrates a strategy for designing a hydrophilic yet ultra-stable MXene via surface grafting with ionomers.

Polybenzimidazole/Mxene composite membranes for intermediate temperature polymer electrolyte membrane fuel cells.

This report demonstrated the first study on the use of a new 2D nanomaterial (Mxene) for enhancing membrane performance of intermediate temperature (>100 °C) polymer electrolyte membrane fuel cells (ITPEMFCs). In this study, a typical Ti3C2T x -MXene was synthesized and incorporated into polybenzimidazole (PBI)-based membranes by using a solution blending method. The composite membrane with 3 wt% Ti3C2T x -MXene showed the proton conductivity more than 2 times higher than that of pristine PBI membrane at the temperature range of 100 °C-170 °C, and led to substantial increase in maximum power density of fuel cells by ∼30% tested at 150 °C. The addition of Ti3C2T x -MXene also improved the mechanical properties and thermal stability of PBI membranes. At 3 wt% Ti3C2T x -MXene, the elongation at break of phosphoric acid doped PBI remained unaffected at 150 °C, and the tensile strength and Young's modulus was increased by ∼150% and ∼160%, respectively. This study pointed out promising application of MXene in ITPEMFCs.

Bijels formed by direct mixing.

By combining interfacial nanoparticles and molecular surfactants together with immiscible liquids of high viscosity, we develop an alternative strategy for creating bicontinuous interfacially jammed emulsion gels (bijels). These bijels are prepared from common ingredients which are widely used in industry: glycerol, silicone oil, silica nanoparticles together with cetyltrimethylammonium bromide (CTAB) surfactant. We tune the sample composition and develop a multi-step mixing protocol to achieve a tortuous arrangement of liquid domains. We show that the nanoparticle location changes from one of the phases to the interface during mixing. The changes in both the microscopic and macroscopic sample configuration after a waiting time of months were assessed. In order for the structure to have long-term stability we find that the densities of the two phases must be similar which we achieved by filling one of the phases with nanoparticle-stabilised droplets of the other. This work paves the way to the production of bijels using fully immiscible liquids and hence their exploitation in many application areas.

Bijels stabilized using rod-like particles.

Bicontinuous interfacially jammed emulsion gels, in short 'bijels', rely on a trapped layer of colloidal particles for their stability. These structures have traditionally been created using spherical colloidal particles. Here we show for the first time the use of rod-shape particles to stabilize bijels. We show that domain size decreases more rapidly with particle concentration in the case of rods compared to spheres. Large-scale analysis and detailed examination of images show that the packing fraction of rods is much higher than expected, in part, due to the role of 'flippers'.

Correction: Bijels stabilized using rod-like particles.

Correction for 'Bijels stabilized using rod-like particles' by Niek Hijnen et al., Soft Matter, 2015, DOI: .

Calibrating ultrasonic sensor measurements of crop canopy heights: a case study of maize and wheat.

Canopy height serves as an important dynamic indicator of crop growth in the decision-making process of field management. Compared with other commonly used canopy height measurement techniques, ultrasonic sensors are inexpensive and can be exposed in fields for long periods of time to obtain easy-to-process data. However, the acoustic wave characteristics and crop canopy structure affect the measurement accuracy. To improve the ultrasonic sensor measurement accuracy, a four-year (2018-2021) field experiment was conducted on maize and wheat, and a measurement platform was developed. A series of single-factor experiments were conducted to investigate the significant factors affecting measurements, including the observation angle (0-60°), observation height (0.5-2.5 m), observation period (8:00-18:00), platform moving speed with respect to the crop (0-2.0 m min-1), planting density (0.2-1 time of standard planting density), and growth stage (maize from three-leaf to harvest period and wheat from regreening to maturity period). The results indicated that both the observation angle and planting density significantly affected the results of ultrasonic measurements (p-value< 0.05), whereas the effects of other factors on measurement accuracy were negligible (p-value > 0.05). Moreover, a double-input factor calibration model was constructed to assess canopy height under different years by utilizing the normalized difference vegetation index and ultrasonic measurements. The model was developed by employing the least-squares method, and ultrasonic measurement accuracy was significantly improved when integrating the measured value of canopy heights and the normalized difference vegetation index (NDVI). The maize measurement accuracy had a root mean squared error (RMSE) ranging from 81.4 mm to 93.6 mm, while the wheat measurement accuracy had an RMSE from 37.1 mm to 47.2 mm. The research results effectively combine stable and low-cost commercial sensors with ground-based agricultural machinery platforms, enabling efficient and non-destructive acquisition of crop height information.

A simple route to enhance the interface between graphite oxide nanoplatelets and a semi-crystalline polymer for stress transfer.

This report shows that thermal treatment is a simple and effective approach to create a polymer crystalline layer on the surface of graphite oxide nanoplatelets (GONPs) in polycaprolactone (PCL) melts. It was found that the crystallization temperature of the PCL increased significantly by nearly 9 degrees C with the incorporation of 2 wt% GONPs. As the composite melts isothermally crystallized at the temperature that was 14 degrees C higher than the crystallization temperature, the polymer crystalline layer was optimized on the surface of the GONPs. At 2 wt% GONPs, the Young's modulus of the composite was nearly 1.5 times greater than for the pure PCL. In comparison with untreated composites, the improvement in the Young's modulus of treated composites nearly doubled. It confirmed that a non-covalent interface for stress transfer can be enhanced by the formation of the polymer crystalline layer bridging the GONPs and the polymer matrix.

The mechanical properties and morphology of a graphite oxide nanoplatelet/polyurethane composite.

Significant reinforcement of polyurethane (PU) using graphite oxide nanoplatelets (GONPs) is reported. Morphologic study shows that, due to the formation of chemical bonding, there is a strong interaction between the GONPs and the hard segment of the PU, which allows effective load transfer. The GONPs can prevent the formation of crystalline hard segments due to their two-dimensional structure. With the incorporation of 4.4 wt% of GONPs, the Young's modulus and hardness of the PU are significantly increased by approximately 900% and approximately 327%, respectively. The resultant high resistance to scratching indicates promise for application of these composite materials in surface coating.

A flexible SERS-active film for studying the effect of non-metallic nanostructures on Raman enhancement.

Since the discovery of surface enhanced Raman scattering (SERS), the choice of SERS-active materials has been limited mainly to metals, especially gold and silver in the visible spectrum. Although non-metals can also be SERS-active by forming nanostructures or composite structures with SERS-active materials, the mechanism behind it is still unclear and there is no perfect technique to study it. In this work, by constructing a SERS structure on a flexible polydimethylsiloxane film, we provide a way to study the effect of non-metallic nanostructures on Raman enhancement by attaching the above film onto flat and nanostructured surfaces. It was found that a nanoporous silicon surface contributes to an additional, up to five times, Raman enhancement. The pore depth and pore size also influence the observed Raman enhancement. These findings will help us not only to understand the mechanism of SERS involving non-metallic nanostructures, but also to design more efficient SERS structures for various applications.

3D assembly of Ti3C2-MXene directed by water/oil interfaces.

MXene is an emerging class of 2D materials exfoliated from ternary carbide and nitride ceramics. The exfoliation process, which is an acid etching approach, functionalizes the MXene surface with -OH, -O and -F groups. These functional groups offer significant opportunities for tuning the colloidal properties of the MXene nanoblocks; importantly, this tunability points the way towards a facile route for assembling these nanoblocks into 3D architectures that are in demand for many applications. This route, presented for the first time here, uses water/oil interfaces for assembling Ti3C2-MXene in 3D architectures. It shows that cetyl trimethylammonium bromide (CTAB) can be used to tune the hydrophilic-hydrophobic balance of Ti3C2-MXene via the interaction of positively charged -N(CH3)3 and -O groups on the MXene surface. Crucially, it is found that this interaction can be controlled via the hydrogen ion concentration in the aqueous phase. Stable oil-in-water emulsions are the only product when the aqueous phase is neutral or basic. This understanding led us to fabricate a high internal phase Pickering emulsion with more than 70 vol% oil droplets and also a solid porous monolith based on this emulsion template.

Stabilizing bijels using a mixture of fumed silica nanoparticles.

Bijels are typically prepared by arresting the phase separation of two liquids using interfacial particles. The surface treatment of the particles is challenging but can be overcome at a cost (Cui et al., Science, 2013, 342, 460-463). Here, we use mixed commercial fumed-silica nanoparticles, giving a facile route to bijel production.

Making non-aqueous high internal phase pickering emulsions: influence of added polymer and selective drying.

We report the first example of a non-aqueous (oil-in-oil) Pickering high internal phase emulsion (HIPE) stabilized by chemically modified fumed silica. In this case, a 75 vol % ethylene carbonate (EC)-rich internal phase is emulsified in 25 vol % p-xylene (xylene)-rich continuous phase using interfacial nanoparticles. It is revealed that no phase inversion takes place during the HIPE formation process when using the appropriate wettability of solid particles. Incorporating polystyrene (PS) into xylene enables one-step formation of PS-filled HIPEs in place of a multi-step polymerization of the continuous phase. We observe that the size of droplets changes with the addition of PS, and we associate this with the change in the viscosity of the continuous xylene-rich phase. Drying the pure HIPE results in the selective removal of xylene and coalescence of EC-rich droplets. With the PS in the xylene-rich continuous phase, we show that EC-rich droplets can be retained even though the xylene is evaporated off, and a new semi-solid composite containing both liquid phase and solid phase is formed via this non-aqueous Pickering-HIPE template.