The crystalline fraction is a critical parameter for assessing the quality of silicon quantum dots(SiQDs),and its enhancement is anticipated to improve the optoelectronic performance of these materials.How-ever,achiev...The crystalline fraction is a critical parameter for assessing the quality of silicon quantum dots(SiQDs),and its enhancement is anticipated to improve the optoelectronic performance of these materials.How-ever,achieving a high crystalline fraction in small-sized SiQDs produced through the pyrolysis of hydro-gen silsesquioxane(HSQ)polymers remains a significant challenge.In this study,we successfully synthe-sized SiQDs with a diameter of 3.24 nm and a crystalline fraction of 98.4%by optimizing the triethoxysi-lane(TES)/aqueous hydrochloric acid(HCl)volume ratio during the hydrolysis-condensation process.The SiQDs exhibited a photoluminescence(PL)center at 764.1 nm and an average PL quantum yield(PLQY)of 24.4%.Our findings demonstrate that the TES/aqueous HCl volume ratio significantly influences the pro-portion of cage structure and the cross-linking density of the network structure in HSQ polymers,which in turn governs SiQD size and crystalline fraction.A high proportion of cage structures in HSQ polymers contributes to high crystallinity.Notably,an increased cross-linking density within the network structure results in higher and more uniform diffusion barriers.This phenomenon not only hinders the diffusion of silicon atoms,which leads to smaller SiQD size,but also facilitates the achievement of high crystalline fraction due to uniform diffusion.This work presents a novel approach to achieving high crystallinity in small SiQDs,with implications for advanced applications in lighting,display technologies,medical imag-ing,and photovoltaics.展开更多
The construction of human settlements plays a vital role in achieving sustainable development goals.With the growing population,both urban and rural planning—as well as the development of human settlements—on the Qi...The construction of human settlements plays a vital role in achieving sustainable development goals.With the growing population,both urban and rural planning—as well as the development of human settlements—on the Qinghai-Tibet Plateau in China have received increasing attention.This study proposed a comprehensive framework to assess the quality of human settlements and identify their limiting factors of Nyingchi City,southeastern Qinghai-Tibet Plateau of China.The framework integrated a region-specific evaluation system tailored to the plateau’s unique characteristics and utilized multi-source data collected through field-based questionnaires and remote sensing.Analytical methods employed include the Criteria Importance Through Intercriteria Correlation(CRITIC)weighting method,difference analysis for evaluating spatial and categorical variations,and a novel approach introduced in this study for identifying limiting factors.In August 2021,a questionnaire-based survey was conducted in the southeastern Qinghai-Tibet Plateau,yielding 823 valid responses.The average evaluation score for human settlement quality(HSQ)was(6.96±0.94),indicating that settlement conditions were approaching the satisfaction threshold.Notably,the score for the health dimension was(6.28±1.41),reflecting relatively underdeveloped health services in the region.From the perspective of spatial patterns,despite its favorable natural conditions,the HSQ in Medog County was relatively backward,reflecting uncoordinated development that warrants attention.Significant differences were observed in the perceptions of human settlements among different groups in terms of ethnicity,income,and educational background.Low ratings for income and employment conditions represented a major limitation to the local HSQ.The development of human settlements in the southeastern Qinghai-Tibet Plateau still needs further promotion due to population disparities and the challenges of creating a healthy environment in high-altitude regions.The results are valuable for improving human settlements in plateau regions,which can help make targeted policy recommendations.展开更多
基金the Sichuan Science and Technology Program(No.2022ZYD0110)the China National Tobacco Corporation Sichuan Company(No.SCYC202120).
文摘The crystalline fraction is a critical parameter for assessing the quality of silicon quantum dots(SiQDs),and its enhancement is anticipated to improve the optoelectronic performance of these materials.How-ever,achieving a high crystalline fraction in small-sized SiQDs produced through the pyrolysis of hydro-gen silsesquioxane(HSQ)polymers remains a significant challenge.In this study,we successfully synthe-sized SiQDs with a diameter of 3.24 nm and a crystalline fraction of 98.4%by optimizing the triethoxysi-lane(TES)/aqueous hydrochloric acid(HCl)volume ratio during the hydrolysis-condensation process.The SiQDs exhibited a photoluminescence(PL)center at 764.1 nm and an average PL quantum yield(PLQY)of 24.4%.Our findings demonstrate that the TES/aqueous HCl volume ratio significantly influences the pro-portion of cage structure and the cross-linking density of the network structure in HSQ polymers,which in turn governs SiQD size and crystalline fraction.A high proportion of cage structures in HSQ polymers contributes to high crystallinity.Notably,an increased cross-linking density within the network structure results in higher and more uniform diffusion barriers.This phenomenon not only hinders the diffusion of silicon atoms,which leads to smaller SiQD size,but also facilitates the achievement of high crystalline fraction due to uniform diffusion.This work presents a novel approach to achieving high crystallinity in small SiQDs,with implications for advanced applications in lighting,display technologies,medical imag-ing,and photovoltaics.
基金Under the auspices of the Second Tibetan Plateau Scientific Expedition and Research Program(STEP,No.2019QZKK0608)。
文摘The construction of human settlements plays a vital role in achieving sustainable development goals.With the growing population,both urban and rural planning—as well as the development of human settlements—on the Qinghai-Tibet Plateau in China have received increasing attention.This study proposed a comprehensive framework to assess the quality of human settlements and identify their limiting factors of Nyingchi City,southeastern Qinghai-Tibet Plateau of China.The framework integrated a region-specific evaluation system tailored to the plateau’s unique characteristics and utilized multi-source data collected through field-based questionnaires and remote sensing.Analytical methods employed include the Criteria Importance Through Intercriteria Correlation(CRITIC)weighting method,difference analysis for evaluating spatial and categorical variations,and a novel approach introduced in this study for identifying limiting factors.In August 2021,a questionnaire-based survey was conducted in the southeastern Qinghai-Tibet Plateau,yielding 823 valid responses.The average evaluation score for human settlement quality(HSQ)was(6.96±0.94),indicating that settlement conditions were approaching the satisfaction threshold.Notably,the score for the health dimension was(6.28±1.41),reflecting relatively underdeveloped health services in the region.From the perspective of spatial patterns,despite its favorable natural conditions,the HSQ in Medog County was relatively backward,reflecting uncoordinated development that warrants attention.Significant differences were observed in the perceptions of human settlements among different groups in terms of ethnicity,income,and educational background.Low ratings for income and employment conditions represented a major limitation to the local HSQ.The development of human settlements in the southeastern Qinghai-Tibet Plateau still needs further promotion due to population disparities and the challenges of creating a healthy environment in high-altitude regions.The results are valuable for improving human settlements in plateau regions,which can help make targeted policy recommendations.
