In this study, the characteristics of nanocellulose extracted from bleached softwood and hardwood pulps by formic acid hydrolysis followed by TEMPO-mediated oxidation were compared using transmission electron microsco...In this study, the characteristics of nanocellulose extracted from bleached softwood and hardwood pulps by formic acid hydrolysis followed by TEMPO-mediated oxidation were compared using transmission electron microscopy(TEM), atomic force microscopy(AFM), Fourier transform infrared analysis(FT-IR), X-ray diffraction(XRD), and thermal gravimetric analysis(TGA). The experimental results showed that the nanocellulose products derived from spruce pulp exhibited a relatively larger particle size, higher crystallinity, and higher thermal stability, compared with the corresponding products obtained from aspen pulp under the same conditions.Furthermore, the study helped establish that the properties of the nanocellulose products were highly dependent on the nature of the starting materials under identical processing conditions.展开更多
Amphiphilic starch derivatives with high content of functional groups were prepared from potato starch using a one-pot synthesis method with a single reaction medium for the entire procedure. Potato starch was benzyla...Amphiphilic starch derivatives with high content of functional groups were prepared from potato starch using a one-pot synthesis method with a single reaction medium for the entire procedure. Potato starch was benzylated, followed by the introduction of hydroxypropyltrimethylammonium(HPMA) moieties without the purification of intermediates. The synthesis was performed under heterogeneous conditions, leading to the formation of benzyl 2-hydroxypropyltri methylammonium starch chloride(BnHPMAS) with a total degree of substitution(DS) of up to 1.4. This process improved the efficiency of the preparation of amphiphilic starch derivatives and reduced the time and resources consumed by avoiding a separation process and purification of the intermediate compounds.The DS of BnHPMAS was in the range of 0.36 to 1.4, which could be tuned by varying the molar ratio of the reagents to repeating unit or by changing the reaction temperature, time, and medium. The structure of the amphiphilic starches was characterized using elemental analysis, size exclusion chromatography,fourier transform infrared spectroscopy(FT-IR), and nuclear magnetic resonance(NMR) spectroscopy. Moreover, the surface tension and turbidity of the solutions of the products were measured for their potential application in the removal of dissolved and colloidal substances in paper cycling water.展开更多
While intramolecular cyclization effectively modulates photoelectronic properties of multi-resonance(MR)-thermally activated delayed fluorescence(TADF)emitters,simultaneous narrowing full width at half maxima(FWHM)of ...While intramolecular cyclization effectively modulates photoelectronic properties of multi-resonance(MR)-thermally activated delayed fluorescence(TADF)emitters,simultaneous narrowing full width at half maxima(FWHM)of spectra and accelerating reverse intersystem crossing(RISC)remain a formidable challenge.Here,we introduce a phosphorus-carbon-bridged cyclization in MR skeletons to synergistically suppress high-frequency molecular vibrations via skeleton rigidification and enhance spin-orbital coupling through introducing heavy-atom effects.Implementing this approach,two blue emitters,phenylphosphine oxide-bridged(BCzBN-PO)and phenylphosphine sulfide-bridged(BCzBN-PS),are developed and exhibit emission peaks at 467 and 474 nm with FWHMs of 19 and 18 nm,respectively.Moreover,benefiting from the additional heavy atom effect of sulfur complementing that of phosphorus,BCzBN-PS achieved a kRISC of 8.5×10^(5)s^(−1),nearly 8-fold higher than that of BCzBN-PO(1.1×10^(5)s^(−1)).In the non-sensitized device architecture,both emitters exhibited narrowband emission with a FWHM<30 nm and a maximum external quantum efficiency(EQE)>20%.Notably,BCzBN-PS,leveraging its higher upconversion rate,demonstrated a superior maximum EQE and lower efficiency roll-off.Furthermore,in the TADF-sensitized device configuration,the organic light-emitting diodes further validated the enhanced upconversion efficiency—evidenced by BCzBN-PS delivering a higher maximum EQE than BCzBN-PO(43.0%vs.41.2%)and a reduced efficiency roll-off(30.1%vs.25.9%at 1000 cd m−2).This work establishes a molecular engineering paradigm that balances color purity and exciton utilization efficiency,paving new avenues for high-performance narrowband electroluminescence.展开更多
In order to improve the accuracy and stability of transplanting machine seedling picking,a seedling pick-up mechanism was designed,which was controlled by a controller and driven by brushless DC servo motor.At the sam...In order to improve the accuracy and stability of transplanting machine seedling picking,a seedling pick-up mechanism was designed,which was controlled by a controller and driven by brushless DC servo motor.At the same time,the parameters of the seedling manipulator were optimized:the mathematical model for the seedling pick-up mechanism was established.According to the predetermined trajectory requirements,the objective function and constraint conditions were proposed,and then the optimal size was obtained by a multi-objective genetic algorithm.At last,Automatic Dynamic Analysis of Mechanical Systems(ADAMS)software was used to simulate and analyze the kinematics and trajectory of the seedling pick-up mechanism,and the mechanism was tested to verify the effectiveness of the mechanism prototype.The experiments showed that the success rate of seedling picking was 94.32%,the rate of acceptably planted seedlings was 96.67%,and the rate of excellently planted seedlings was 63.48%.展开更多
基金the Johan GadolinScholarship Programme at the Johan Gadolin Process Chemistry Centre at Abo Akademi University (Finland)the National Natural Science Foundation of China (No. 31470609)
文摘In this study, the characteristics of nanocellulose extracted from bleached softwood and hardwood pulps by formic acid hydrolysis followed by TEMPO-mediated oxidation were compared using transmission electron microscopy(TEM), atomic force microscopy(AFM), Fourier transform infrared analysis(FT-IR), X-ray diffraction(XRD), and thermal gravimetric analysis(TGA). The experimental results showed that the nanocellulose products derived from spruce pulp exhibited a relatively larger particle size, higher crystallinity, and higher thermal stability, compared with the corresponding products obtained from aspen pulp under the same conditions.Furthermore, the study helped establish that the properties of the nanocellulose products were highly dependent on the nature of the starting materials under identical processing conditions.
基金financially supported by National Natural Science Foundation of China (No. 21774036)State Key Laboratory of Pulp and Paper Engineering (No. 2017TS01)
文摘Amphiphilic starch derivatives with high content of functional groups were prepared from potato starch using a one-pot synthesis method with a single reaction medium for the entire procedure. Potato starch was benzylated, followed by the introduction of hydroxypropyltrimethylammonium(HPMA) moieties without the purification of intermediates. The synthesis was performed under heterogeneous conditions, leading to the formation of benzyl 2-hydroxypropyltri methylammonium starch chloride(BnHPMAS) with a total degree of substitution(DS) of up to 1.4. This process improved the efficiency of the preparation of amphiphilic starch derivatives and reduced the time and resources consumed by avoiding a separation process and purification of the intermediate compounds.The DS of BnHPMAS was in the range of 0.36 to 1.4, which could be tuned by varying the molar ratio of the reagents to repeating unit or by changing the reaction temperature, time, and medium. The structure of the amphiphilic starches was characterized using elemental analysis, size exclusion chromatography,fourier transform infrared spectroscopy(FT-IR), and nuclear magnetic resonance(NMR) spectroscopy. Moreover, the surface tension and turbidity of the solutions of the products were measured for their potential application in the removal of dissolved and colloidal substances in paper cycling water.
基金supported by the National Natural Science Foundation of China(52222308 and 22135004)the National Key Research and Development Program(2023YFE0203300 and 2024YFB3612100)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(2021B1515120041)the Open Project Program of Wuhan National Laboratory for Optoelectronics(2023WNLOKF010)the National Natural Science Foundation of China’s Youth Project for Doctoral Students(524B2035).
文摘While intramolecular cyclization effectively modulates photoelectronic properties of multi-resonance(MR)-thermally activated delayed fluorescence(TADF)emitters,simultaneous narrowing full width at half maxima(FWHM)of spectra and accelerating reverse intersystem crossing(RISC)remain a formidable challenge.Here,we introduce a phosphorus-carbon-bridged cyclization in MR skeletons to synergistically suppress high-frequency molecular vibrations via skeleton rigidification and enhance spin-orbital coupling through introducing heavy-atom effects.Implementing this approach,two blue emitters,phenylphosphine oxide-bridged(BCzBN-PO)and phenylphosphine sulfide-bridged(BCzBN-PS),are developed and exhibit emission peaks at 467 and 474 nm with FWHMs of 19 and 18 nm,respectively.Moreover,benefiting from the additional heavy atom effect of sulfur complementing that of phosphorus,BCzBN-PS achieved a kRISC of 8.5×10^(5)s^(−1),nearly 8-fold higher than that of BCzBN-PO(1.1×10^(5)s^(−1)).In the non-sensitized device architecture,both emitters exhibited narrowband emission with a FWHM<30 nm and a maximum external quantum efficiency(EQE)>20%.Notably,BCzBN-PS,leveraging its higher upconversion rate,demonstrated a superior maximum EQE and lower efficiency roll-off.Furthermore,in the TADF-sensitized device configuration,the organic light-emitting diodes further validated the enhanced upconversion efficiency—evidenced by BCzBN-PS delivering a higher maximum EQE than BCzBN-PO(43.0%vs.41.2%)and a reduced efficiency roll-off(30.1%vs.25.9%at 1000 cd m−2).This work establishes a molecular engineering paradigm that balances color purity and exciton utilization efficiency,paving new avenues for high-performance narrowband electroluminescence.
基金This research was supported by the National Natural Science Foundation of China(Grant No.51775104).
文摘In order to improve the accuracy and stability of transplanting machine seedling picking,a seedling pick-up mechanism was designed,which was controlled by a controller and driven by brushless DC servo motor.At the same time,the parameters of the seedling manipulator were optimized:the mathematical model for the seedling pick-up mechanism was established.According to the predetermined trajectory requirements,the objective function and constraint conditions were proposed,and then the optimal size was obtained by a multi-objective genetic algorithm.At last,Automatic Dynamic Analysis of Mechanical Systems(ADAMS)software was used to simulate and analyze the kinematics and trajectory of the seedling pick-up mechanism,and the mechanism was tested to verify the effectiveness of the mechanism prototype.The experiments showed that the success rate of seedling picking was 94.32%,the rate of acceptably planted seedlings was 96.67%,and the rate of excellently planted seedlings was 63.48%.
