Derivatization has great potential for the high-value utilization of cellulose by enhancing its processability and functionality.However,due to the low reactivity of natural cellulose,it remains challenging to rapidly...Derivatization has great potential for the high-value utilization of cellulose by enhancing its processability and functionality.However,due to the low reactivity of natural cellulose,it remains challenging to rapidly prepare cellulose derivatives with high degrees of substitution.The“cavitation effect”of ultrasound can reduce the particle size and crystalline index of cellulose,which provides a possible method for preparing cellulose derivatives.Herein,a feasible method was proposed for efficiently converting regenerated cellulose to cellulose oleate with the assistance of ultrasonic treatment.By adjusting the reaction conditions including ultrasonic intensity,feeding ratios of oleic acid,reaction time,and reaction solvent,a series of cellulose oleates with degrees of substitution ranging from 0.37 to 1.71 were synthesized.Additionally,the effects of different reaction conditions on the chemical structures,crystalline structures,and thermal behaviors were investigated thoroughly.Cellulose oleates with degrees of substitution exceeding 1.23 exhibited amorphous structures and thermoplasticity with glass transition temperatures at 159.8 to 172.6℃.This study presented a sustainable and practicable method for effectively derivatizing cellulose.展开更多
In this paper,an ultrasound with frequency of 815 kHz was used to re-search the sonochemical yield in a small-size reverberation field by the methodof fluorescent spectrum analysis.There are two characteristics on the...In this paper,an ultrasound with frequency of 815 kHz was used to re-search the sonochemical yield in a small-size reverberation field by the methodof fluorescent spectrum analysis.There are two characteristics on the effect ofsonochemistry in the reverberation field:First,the cavitation threshold wasabout 0.3W/cm^2(it was 0.7W/cm^2 in travelling field);Second,when thesound intensity was larger than the threshold,the sonochemical yield increasedas the intensity increased and increased rapidly after the intensity was at1.69-2.13W/cm^2,so that there was a upturned point in the curve of the result(which would tend to saturation in the travelling field).The theoretical analysisshows that the reason of the threshold decrease is that the sound energy densitybecomes high in the reverberation field,and the upturned point results from thedisturbance of the radiation pressure on the liquid surface.Therefore,by exper-iment and theory this paper shows that a reverberation field has to be built forthe higher展开更多
The sonochemical effect of a bifrequency orthogonal ultrasonic irradiation has been studied by using two different detecting methods. It has been shown that the sonochemical yield produced by the bifrequency irradiati...The sonochemical effect of a bifrequency orthogonal ultrasonic irradiation has been studied by using two different detecting methods. It has been shown that the sonochemical yield produced by the bifrequency irradiation appears to be much more than the sum of the yields produced separately by the two irradiations. The bifrequency irradiation, therefore, can be expected to exert a great influence on the development of sonohemical展开更多
In this study we examined the cytotoxic effect of ZnO nanoparticles on various human cancer and normal cells.We found that the ZnO nanoparticles exerted a cytotoxic effect on the human glioma cell lines A172,U87,LNZ30...In this study we examined the cytotoxic effect of ZnO nanoparticles on various human cancer and normal cells.We found that the ZnO nanoparticles exerted a cytotoxic effect on the human glioma cell lines A172,U87,LNZ308,LN18,and LN229,whereas no cytotoxic effect was observed on normal human astrocytes.Similarly,the ZnO nanoparticles induced cell death in breast and prostate cancer cell lines while no major effect was observed in the respective normal breast and prostate cell lines.Using the fl uorescent dye 2,7-dichlorofl uorescein diacetate,we found that treatment of the glioma cells with ZnO nanoparticles induced a large increase in the generation of reactive oxygen species(ROS)and treatment of the cells with N-acetyl cysteine decreased the cytotoxic effect of the ZnO nanoparticles.In contrast,a smaller effect on ROS generation was observed in the normal astrocytes.These results suggest that ZnO nanoparticles may be employed as a selective cytotoxic agent for the eradication of cancer cells.展开更多
Sonochemical synthesis has flourished significantly in the last few decades for the preparation of photocatalysts.A large number of photocatalysts have been prepared through sonochemical techniques.This review highlig...Sonochemical synthesis has flourished significantly in the last few decades for the preparation of photocatalysts.A large number of photocatalysts have been prepared through sonochemical techniques.This review highlights the scope of sonochemistry in the preparation of photocatalysts,and their applications in energy production and environmental remediation.Beside,the sonochemical degradation of pollutants is discussed in detail.The progress made in sonochemical synthesis and the future perspective for this technique are summarized here.This review may create more enthusiasm among researchers to pay extra attention to the sonochemical synthesis of materials and add their useful contribution to the investigation of new materials for photocatalytic and other applications.This will propel this technique toward commercial sonosynthesis of nanomaterials.展开更多
Silver nanoparticles (AgNPs) are directly grown on surface of ~25 μm copper wire by ultrasound-assisted chemical reduction. Silver nitrate is used as precursors, when polyvinylpyrrolidone (PVP) is added as a controll...Silver nanoparticles (AgNPs) are directly grown on surface of ~25 μm copper wire by ultrasound-assisted chemical reduction. Silver nitrate is used as precursors, when polyvinylpyrrolidone (PVP) is added as a controller of the dimension of AgNPs. Influence of growth parameters such as precursor's concentration, ratio proportion of PVP and ultra-sonication on the growth of AgNPs coating are determined. The best morphology, size of the AgNPs are observed on copper wire. The results show that the copper wire coated with AgNPs of^100 nm diameter exhibits good antioxidation and ohmic contact after sinter on Si substrate at a temperature as low as 320℃, is especially suitable as a substitute for silver paste electrode used in silicon solar cells.展开更多
基金The authors are grateful for financial support from the National Natural Science Foundation of China(Grant Nos.52273040 and 51873128)Yunnan Fundamental Research Projects(Grant No.202301AT070232).
文摘Derivatization has great potential for the high-value utilization of cellulose by enhancing its processability and functionality.However,due to the low reactivity of natural cellulose,it remains challenging to rapidly prepare cellulose derivatives with high degrees of substitution.The“cavitation effect”of ultrasound can reduce the particle size and crystalline index of cellulose,which provides a possible method for preparing cellulose derivatives.Herein,a feasible method was proposed for efficiently converting regenerated cellulose to cellulose oleate with the assistance of ultrasonic treatment.By adjusting the reaction conditions including ultrasonic intensity,feeding ratios of oleic acid,reaction time,and reaction solvent,a series of cellulose oleates with degrees of substitution ranging from 0.37 to 1.71 were synthesized.Additionally,the effects of different reaction conditions on the chemical structures,crystalline structures,and thermal behaviors were investigated thoroughly.Cellulose oleates with degrees of substitution exceeding 1.23 exhibited amorphous structures and thermoplasticity with glass transition temperatures at 159.8 to 172.6℃.This study presented a sustainable and practicable method for effectively derivatizing cellulose.
基金Project is supported by the National Natural Science foundation of China the work has been finished in the labouratory of Modern Acoustics,Nanjing University,Nanjing
文摘In this paper,an ultrasound with frequency of 815 kHz was used to re-search the sonochemical yield in a small-size reverberation field by the methodof fluorescent spectrum analysis.There are two characteristics on the effect ofsonochemistry in the reverberation field:First,the cavitation threshold wasabout 0.3W/cm^2(it was 0.7W/cm^2 in travelling field);Second,when thesound intensity was larger than the threshold,the sonochemical yield increasedas the intensity increased and increased rapidly after the intensity was at1.69-2.13W/cm^2,so that there was a upturned point in the curve of the result(which would tend to saturation in the travelling field).The theoretical analysisshows that the reason of the threshold decrease is that the sound energy densitybecomes high in the reverberation field,and the upturned point results from thedisturbance of the radiation pressure on the liquid surface.Therefore,by exper-iment and theory this paper shows that a reverberation field has to be built forthe higher
文摘The sonochemical effect of a bifrequency orthogonal ultrasonic irradiation has been studied by using two different detecting methods. It has been shown that the sonochemical yield produced by the bifrequency irradiation appears to be much more than the sum of the yields produced separately by the two irradiations. The bifrequency irradiation, therefore, can be expected to exert a great influence on the development of sonohemical
文摘In this study we examined the cytotoxic effect of ZnO nanoparticles on various human cancer and normal cells.We found that the ZnO nanoparticles exerted a cytotoxic effect on the human glioma cell lines A172,U87,LNZ308,LN18,and LN229,whereas no cytotoxic effect was observed on normal human astrocytes.Similarly,the ZnO nanoparticles induced cell death in breast and prostate cancer cell lines while no major effect was observed in the respective normal breast and prostate cell lines.Using the fl uorescent dye 2,7-dichlorofl uorescein diacetate,we found that treatment of the glioma cells with ZnO nanoparticles induced a large increase in the generation of reactive oxygen species(ROS)and treatment of the cells with N-acetyl cysteine decreased the cytotoxic effect of the ZnO nanoparticles.In contrast,a smaller effect on ROS generation was observed in the normal astrocytes.These results suggest that ZnO nanoparticles may be employed as a selective cytotoxic agent for the eradication of cancer cells.
基金financially supported by National Science Foundation of China(No.51602207)。
文摘Sonochemical synthesis has flourished significantly in the last few decades for the preparation of photocatalysts.A large number of photocatalysts have been prepared through sonochemical techniques.This review highlights the scope of sonochemistry in the preparation of photocatalysts,and their applications in energy production and environmental remediation.Beside,the sonochemical degradation of pollutants is discussed in detail.The progress made in sonochemical synthesis and the future perspective for this technique are summarized here.This review may create more enthusiasm among researchers to pay extra attention to the sonochemical synthesis of materials and add their useful contribution to the investigation of new materials for photocatalytic and other applications.This will propel this technique toward commercial sonosynthesis of nanomaterials.
基金financially supported by the National Natuie Science Foundation of China (No 11204082)Shanghai Natural Pond (No, 16ZR1410700)
文摘Silver nanoparticles (AgNPs) are directly grown on surface of ~25 μm copper wire by ultrasound-assisted chemical reduction. Silver nitrate is used as precursors, when polyvinylpyrrolidone (PVP) is added as a controller of the dimension of AgNPs. Influence of growth parameters such as precursor's concentration, ratio proportion of PVP and ultra-sonication on the growth of AgNPs coating are determined. The best morphology, size of the AgNPs are observed on copper wire. The results show that the copper wire coated with AgNPs of^100 nm diameter exhibits good antioxidation and ohmic contact after sinter on Si substrate at a temperature as low as 320℃, is especially suitable as a substitute for silver paste electrode used in silicon solar cells.
