Er^3＋ doped SrTiO3 ultrafine powders were prepared by solid state reaction in a molten NaCl flux. The structural properties were characterized by X-ray diffraction, field emission scanning electron microscopy, and Fo...Er^3＋ doped SrTiO3 ultrafine powders were prepared by solid state reaction in a molten NaCl flux. The structural properties were characterized by X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. The Stokes emission spectra of Er^3＋ in SrTiO3：Er^3＋ ranging from green to near infrared region were investigated under 514.5 nm laser excitation. The green and red upconverted luminescence spectra of Er^3＋ were measured under excitation into the 419/2 level by 785 nm laser. The upconversion mechanisms were studied in detail through laser power dependence and Er^3＋ ion concentration dependence of upconverted emissions, and results show that excited state absorption and energy transfer process are the possible mechanisms for the upconversion. The upconversion properties indicate that SrTiO3：Er^3＋ may be used in upconversion phosphors.展开更多
Syndrome differentiation-based treatment is one of the key characteristics of Traditional Chinese Medicine(TCM).The process of syndrome differentiation is difficult and challenging due to its complexity,diversity and ...Syndrome differentiation-based treatment is one of the key characteristics of Traditional Chinese Medicine(TCM).The process of syndrome differentiation is difficult and challenging due to its complexity,diversity and vagueness.Analyzing syndrome principles from historical records of TCM using data mining(DM)technology has been of high interest in recent years.Nevertheless,in most relevant studies,existing DM algorithms have been simply developed for TCM mining,while the combination of TCM theories or its characteristics with DM algorithms has rarely been reported.This paper presents a novel Symptom-Syndrome Topic Model(SSTM),which is a supervised probabilistic topic model with three-tier Bayesian structure.In the SSTM,syndromes are considered as observed topic labels to distinguish certain symptoms from possible symptoms according to their different positions.The generation of our model is in full compliance with the syndrome differentiation theory of TCM.Experimental results show that the SSTM is more effective than other models for syndrome differentiating.展开更多
[ Objective ] This study aimed to optimize the extraction technology for rice bran oil. [ Method ] Using rice bran as raw material, effects of ultrasonicassisted extraction technology and different organic solvents, e...[ Objective ] This study aimed to optimize the extraction technology for rice bran oil. [ Method ] Using rice bran as raw material, effects of ultrasonicassisted extraction technology and different organic solvents, extraction durations, solid-liquid ratios and extraction temperatures on extraction results of rice bran oil were investigated. Based on the results of single-factor experiment, L9 （34 ） orthngonal experiment with three factors at three levels was conducted to optimize the extraction technological parameters, thus obtaining the optimal technological conditions for extracting rice bran oil. [ Result] Anhydrous ethanol led to the best extraction result; after ultrasonic treatment, the extraction rate of rice bran oil from raw material was not enhanced. The optimized technological parameters were ： extraction temperature of 80 ℃, extraction duration of 20 rain and solid-liquid ratio of 1：24 （ g： ml）. Under the optimized technological conditions, the extraction rate of rice bran oil reached 19.33%. [ Conclusion] This study laid solid foundation for further investigation and development of rice bran oil.展开更多
Air samples were collected simultaneously at platform,mezzanine and outdoor in five typical stations of subway system in Shanghai,China using stainless steel canisters and analyzed by gas chromatography-mass selective...Air samples were collected simultaneously at platform,mezzanine and outdoor in five typical stations of subway system in Shanghai,China using stainless steel canisters and analyzed by gas chromatography-mass selective detector （GC-MSD） after cryogenic pre-concentration.Benzene,toluene,ethylbenzene and xylenes （BTEX） at the platforms and mezzanines inside the stations averaged （10.3±2.1）,（38.7±9.0）,（19.4±10.1） and （30.0±11.1） μg/m 3,respectively;while trichloroethylene （TrCE）,tetrachloroethylene （TeCE） and para-dichlorobenzene （pDCB）,vinyl chloride and carbon tetrachloride were the most abundant chlorinated hydrocarbons inside the stations with average levels of （3.6±1.3）,（1.3±0.5）,（4.1±1.1）,（2.2±1.1） and （1.2±0.3） μg/m 3,respectively.Mean levels of major aromatic and chlorinated hydrocarbons were higher indoor （platforms and mezzanines） than outdoor with average indoor/outdoor （I/O） ratios of 1.1–9.5,whereas no significant indoor/outdoor differences were found except for benzene and TrCE.The highly significant mutual correlations （p0.01） for BTEX between indoor and outdoor and their significant correlation （p0.05） with methyl tert-butyl ether （MTBE）,a marker of traffic-related emission without other indoor and outdoor sources,indicated that BTEX were introduced into the subway stations from indoor/outdoor air exchange and traffic emission should be their dominant source.TrCE and pDCB were mainly from indoor emission and TeCE might have both indoor emission sources and contribution from outdoor air,especially in the mezzanines.展开更多
Dual-excitation and dual-emission Y_(4)GeO_(8):Bi^(3+),Sm^(3+)phosphors were manufactured by traditional solidphase sintering technique.The X-ray diffraction,morphology,photoluminescence,energy transfer process and te...Dual-excitation and dual-emission Y_(4)GeO_(8):Bi^(3+),Sm^(3+)phosphors were manufactured by traditional solidphase sintering technique.The X-ray diffraction,morphology,photoluminescence,energy transfer process and temperature sensing properties of Y_(4)GeO_(8):Bi^(3+),Sm^(3+)samples were comprehensively evaluated.The Y4GeO_(8):Bi^(3+),Sm^(3+)phosphors exhibit characteristic emissions of Bi^(3+)(^(3)P_(1)→^(1)S_(0)) and Sm^(3+)(^(4)G_(5/2)→^(6)H)under both 290 and 347 nm excitations.In fluorescence intensity ratio and Commission International de L'Eclairage coordinates modes,Y_(4)GeO_(8):Bi^(3+),Sm^(3+)samples present excellent temperature measurement performance.The maximum relative sensitivity(S_(r-max)) values of the former are 1.55%/K(460 K,290 nm excitation) and 0.82%/K(506 K,347 nm excitation).The S_(r-max)(x) values of the latter are 0.21 %/K(437 K,290 nm excitation) and 0.15%/K(513 K,347 nm excitation).These results illustrate that Y_(4)GeO_(8):Bi^(3+),Sm^(3+)phospho rs can be used as a candidate material for a dual-mode optical thermometer under dual-excitation.展开更多
In this work,a group of Bi^(3+)/Eu^(3+)-doped SiO2-Al_(2)O_(3)-MCO_(3)(M=Ca,Sr,Ba) glasses were fabricated through melt-quenching method.Their structure and photoluminescence characters were studied via Xray diffracti...In this work,a group of Bi^(3+)/Eu^(3+)-doped SiO2-Al_(2)O_(3)-MCO_(3)(M=Ca,Sr,Ba) glasses were fabricated through melt-quenching method.Their structure and photoluminescence characters were studied via Xray diffraction(XRD),UV-Vis transmission spectra(TRS),excitation spectra,emission spectra and decay lifetimes.The XRD results show that no nano-crystal phase forms in glass matrix with different doping concentrations of Bi^(3+)and Eu^(3+)ions.Through regulating optical alkalinity value,the intensity of Bi^(3+)ions increases and the peak position shifts to red wavelength.The Bi^(3+)/Eu^(3+) co-doped glasses show a blue-white-yellow-red luminescence by changing concentration of Eu^(3+) ions.Energy transfer efficiency from Bi^(3+) to Eu^(3+) can reach as high as 10.54%.At 423 K, the emission intensity of 55SiO_(2)-10Al_(2)O_(3)-35BaO-0.25Bi_(2)O_(3)(GBE0.5) is 31.1% of that at 308 K.Meanwhile,the activation energy of the glass matrix is 0.251 eV.All results suggest that these Bi^(3+)/Eu^(3+) co-doped glass samples possess potential application in LED field.展开更多
Ozone(O_(3))pollution is usually linked to warm weather and strong solar radiation,making it uncommon in cold winters.However,an unusual occurrence of four high O_(3)episode days(with maximum hourly concentrations exc...Ozone(O_(3))pollution is usually linked to warm weather and strong solar radiation,making it uncommon in cold winters.However,an unusual occurrence of four high O_(3)episode days(with maximum hourly concentrations exceeding 100 ppbv and peaking at 121 ppbv)was recorded in January 2018 in Lanzhou city,China.During these episodes,the average daytime concentration of total non-methane volatile organic compounds(TVOCs)reached 153.4±19.0 ppbv,with alkenes—largely emitted from the local petrochemical industry—comprising 82.3±13.1 ppbv.Here we show a photochemical box model coupled with a Master Chemical Mechanism to elucidate the mechanisms behind this unusual wintertime O_(3)pollution.We find that the typically low temperatures(−1.7±1.3℃)and weak solar radiation(263.6±60.7 W m^(-2))of those winter episode days had a minimal effect on the reactivity of VOCs with OH radicals.Instead,the ozonolysis of alkenes generated Criegee intermediates,which rapidly decomposed into substantial ROx radicals(OH,HO_(2),and RO_(2))without sunlight.This radical production led to the oxidation of VOCs,with alkene ozonolysis ultimately contributing to 89.6±8.7%of the O_(3)formation during these episodes.This mechanism did not activate at night due to the depletion of O_(3)by the NO titration effect.Furthermore,the findings indicate that a reduction of alkenes by 28.6%or NO_(x)by 27.7%in the early afternoon could significantly mitigate wintertime O_(3)pollution.Overall,this study unravels the unique mechanism of alkene-induced winter O_(3)pollution and offers a reference for winter O_(3)reduction strategies in the petrochemical industrial regions.展开更多
Land-sea atmosphere interaction(LSAI)is one of the important processes affecting ozone(O_(3))pollution in coastal areas.The effects of small-scale LSAIs like sea-land breezes have been widely studied.However,it is not...Land-sea atmosphere interaction(LSAI)is one of the important processes affecting ozone(O_(3))pollution in coastal areas.The effects of small-scale LSAIs like sea-land breezes have been widely studied.However,it is not fully clear how and to what extent the large-scale LSAIs affect O_(3) pollution.Here we explored an O_(3) episode to illuminate the role of large-scale LSAIs in O_(3) pollution over the BohaieYellow Seas and adjacent areas through observations and model simulations.The results show that the northern Bohai Sea's coastal region,influenced by the Mongolian High,initially experienced a typical unimodal diurnal O_(3) variation for three days,when O_(3) precursors from BeijingeTianjineHebei,Shandong,and Northeast China were transported to the BohaieYellow Seas.Photochemical reactions generated O_(3) within marine air masses,causing higher O_(3) levels over the seas than coastal regions.As the Mongolian High shifted eastward and expanded,southerly winds on its western edge transported O_(3)-rich marine air masses toward the coast,prolonging pollution for an additional three days and weakening diurnal variations.Subsequently,emissions from the Korean Peninsula and marine shipping significantly affected O_(3) levels in the northern Bohai Sea(10.7%and 13.7%,respectively).Notably,Shandong's emissions played a substantial role in both phases(27.5%and 26.1%,respectively).These findings underscore the substantial impact of large-scale LSAIs driven by the Mongolian High on O_(3) formation and pollution duration in coastal cities.This insight helps understand and manage O_(3) pollution in northern Bohai Sea cities and broadly applies to temperate coastal cities worldwide.展开更多
The combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change.Yet,the risk of urban overheating can be mitigated b...The combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change.Yet,the risk of urban overheating can be mitigated by urban green-blue-grey infrastructure(GBGI),such as parks,wetlands,and engineered greening,which have the potential to effectively reduce summer air temperatures.Despite many reviews,the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear.This systematic literature review synthesizes the evidence base for heat mitigation and related co-benefits,identifies knowledge gaps,and proposes recommendations for their implementation to maximize their benefits.After screening 27,486 papers,202 were reviewed,based on 51 GBGI types categorized under 10 main divisions.Certain GBGI(green walls,parks,street trees)have been well researched for their urban cooling capabilities.However,several other GBGI have received negligible(zoological garden,golf course,estuary)or minimal(private garden,allotment)attention.The most efficient air cooling was observed in botanical gardens(5.0±3.5℃),wetlands(4.9±3.2℃),green walls(4.1±4.2℃),street trees(3.8±3.1℃),and vegetated balconies(3.8±2.7℃).Under changing climate conditions(2070–2100)with consideration of RCP8.5,there is a shift in climate subtypes,either within the same climate zone(e.g.,Dfa to Dfb and Cfb to Cfa)or across other climate zones(e.g.,Dfb[continental warm-summer humid]to BSk[dry,cold semi-arid]and Cwa[temperate]to Am[tropical]).These shifts may result in lower efficiency for the current GBGI in the future.Given the importance of multiple services,it is crucial to balance their functionality,cooling performance,and other related co-benefits when planning for the future GBGI.This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritizing effective interventions to reduce the risk of urban overheating,filling research gaps,and promoting community resilience.展开更多
We present the continuously measurements of volatile organic compounds(VOCs)at a receptor site(Wan Qing Sha,WQS)in the Pearl River Delta(PRD)region from September to November of 2017.The average mixing ratios of total...We present the continuously measurements of volatile organic compounds(VOCs)at a receptor site(Wan Qing Sha,WQS)in the Pearl River Delta(PRD)region from September to November of 2017.The average mixing ratios of total VOCs(TVOCs)was 36.3±27.9 ppbv with the dominant contribution from alkanes(55.5%),followed by aromatics(33.3%).The diurnal variation of TVOCs showed a strong photochemical consumption during daytime,resulting in the formation of ozone(O_(3)).Five VOC sources were resolved by the positive matrix factorization(PMF)model,including solvent usage(28.6%),liquid petroleum gas(LPG)usage(24.4%),vehicle exhaust(21.0%),industrial emissions(13.2%)and gasoline evaporation(12.9%).The regional transport air masses from the upwind cities of south China can result in the elevated concentrations of TVOCs.Low ratios of TVOCs/NO_(x)(1.53±0.88)suggested that the O_(3) formation regime at WQS site was VOC-limited,which also confirmed by a photochemical box model with the master chemical mechanism(PBM-MCM).Furthermore,the observation on high-O_(3) episode days revealed that frequent O_(3) outbreaks at WQS were mainly caused by the regional transport of anthropogenic VOCs especially for aromatics and the subsequent photochemical reactions.This study provides valuable information for policymakers to propose the effective control strategies on photochemical pollution in a regional perspective.展开更多
Herein,we reported novel Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors elaborated via conventional solid-state reaction.and we further explored their properties as optical thermometer by using fluorescence intensity ratio(FIR...Herein,we reported novel Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors elaborated via conventional solid-state reaction.and we further explored their properties as optical thermometer by using fluorescence intensity ratio(FIR)method complemented by detailed analysis on crystal structure,up-conversion luminescence and energy transfer from Yb^(3+)to Er^(3+).Upon 980 nm laser excitation,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors present525,547 and 659 nm emission bands assigned to the characteristic transitions of Er^(3+).Furthermore,Y_(4)GeO_(8):Er^(3+),Yb^(3+)samples show outstanding temperature sensing performances.To be specific,the minimal temperature resolution is 0.03 K(303 K),and the relative sensitivity of FIR can be up to 1.152%/K(303 K).Hence,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors can be possible candidates for thermometry devices.展开更多
Objective:There are many reports on associations between spermatogenesis and partial azoospermia factor c(AZFc) deletions as well as duplications;however,results are conflicting,possibly due to differences in methodol...Objective:There are many reports on associations between spermatogenesis and partial azoospermia factor c(AZFc) deletions as well as duplications;however,results are conflicting,possibly due to differences in methodology and ethnic background.The purpose of this study is to investigate the association of AZFc polymorphisms and male infertility in the Yi ethnic population,residents within Yunnan Province,ChinaMethods:A total of 224 infertile patients and 153 fertile subjects were selected in the Yi ethnic population.The study was performed by sequence-tagged site plus/minus(STS+/) analysis followed by gene dosage and gene copy definition analysis.Y haplotypes of 215 cases and 115 controls were defined by 12 binary markers using single nucleotide polymorphism on Y chromosome(Y-SNP) multiplex assays based on single base primer extension technology.Results:The distribution of Y haplotypes was not significantly different between the case and control groups.The frequencies of both gr/gr(7.6% vs.8.5%) and b2/b3(6.3% vs.8.5%) deletions do not show significant differences.Similarly,single nucleotide variant(SNV) analysis shows no significant difference of gene copy definition between the cases and controls.However,the frequency of partial duplications in the infertile group(4.0%) is significantly higher than that in the control group(0.7%).Further,we found a case with sY1206 deletion which had two CDY1 copies but removed half of DAZ genes.Conclusions:Our results show that male infertility is associated with partial AZFc duplications,but neither gr/gr nor b2/b3 deletions,suggesting that partial AZFc duplications rather than deletions are risk factors for male infertility in Chinese-Yi population.展开更多
Single-phase Y_(2)BaAl_(4)SiO_(12):Tb^(3+),Eu^(3+)phosphors with adjustable luminescence were successfully prepared by high-temperature solid-state reaction method.The structural,luminescent properties and ene rgy tra...Single-phase Y_(2)BaAl_(4)SiO_(12):Tb^(3+),Eu^(3+)phosphors with adjustable luminescence were successfully prepared by high-temperature solid-state reaction method.The structural,luminescent properties and ene rgy transfer(ET) process of Y_(2)BaAl_(4)SiO_(12):Tb^(^(3+)),Eu^(3+)phosphors were syste matically analyzed with the help of X-ray diffraction(XRD),scanning electron microscopy(SEM),excitation spectra,emission spectra and photoluminescence decay curves.Tunable luminescence ranging from green through yellow and definitively to red can be achieved by elevating amounts of Eu^(3+)ions in Tb^(3+),Eu^(3+)co-doped samples.Besides,the ET mechanism and efficiency were also analyzed and the maximum ET efficiency is 67%.All the results show that Y_(2)BaAl_(4)SiO_(12):Tb^(3+),Eu^(3+)phosphors can be used in solid-state lighting.展开更多
The multi-pass scheduling method is a key issue in die-less spinning for determining the quality of the final products, including their shape deviations and wall thicknesses, and has drawn increasing interest in recen...The multi-pass scheduling method is a key issue in die-less spinning for determining the quality of the final products, including their shape deviations and wall thicknesses, and has drawn increasing interest in recent studies devoted to trying to improve the accuracy of the formed parts. In this paper, two main parameters, roller path profiles and deformation allocations in each pass, are considered in newly proposed multi-pass scheduling and optimizing methods in die-less spinning. Four processing methods with different roller path profiles and with three deformation allocation methods are proposed for investigating the influence of scheduling parameters on product qualities. The ＇similar geometry principle for restraining shape deviation＇ and the ＇small curvature principle for maintaining wall thickness＇ are presented for optimal design of roller path profiles; in addition, the ＇uniform allocation principle for maintaining wall thickness＇ and the ＇large deformation principle for restraining shape deviation＇ are brought forward as suggestions for deformation allocations. Based on these principles, a scheduling method denoted by RF＋（FP ＆ EHS） is presented to improve the comprehensive quality of a product of die-less spinning.展开更多
Layered carbon materials(LCMs)are composed of basic carbon layer units,such as graphite,soft carbon,hard carbon,and graphene.While they have been widely applied in the anode of potassium-ion batteries,the potassium st...Layered carbon materials(LCMs)are composed of basic carbon layer units,such as graphite,soft carbon,hard carbon,and graphene.While they have been widely applied in the anode of potassium-ion batteries,the potassium storage mechanisms and performances of various LCMs are isolated and difficult to relate to each other.More importantly,there is a lack of a systematic understanding of the correlation between the basic microstructural unit(crystallinity and defects)and the potas-sium storage behavior.In this review,we explored the key structural factors affecting the potassium storage in LCMs,namely,the crystallinity and defects of carbon layers,and the key parameters(L_(a),L_(c),d_(002),I_(D)/I_(G))that characterize the crystallinity and defects of different carbon materials were extracted from various databases and literature sources.A structure–property database of LCMs was thus built,and the effects of these key structural parameters on the potassium storage properties,including the capacity,the rate and the working voltage plateau,were systematically analyzed.Based on the structure–prop-erty database analysis and the guidance of thermodynamics and kinetics,a relationship between various LCMs and potas-sium storage properties was established.Finally,with the help of machine learning,the key structural parameters of layered carbon anodes were used for the first time to predict the potassium storage performance so that the large amount of research data in the database could more effectively guide the scientific research and engineering application of LCMs in the future.展开更多
With narrow red photoluminescence (PL) bands, tetravalent Mn^(4+) doped phosphors show promising prospect in commercial application to effectively expand color gamut of phosphor converted LED displays. Here, we report...With narrow red photoluminescence (PL) bands, tetravalent Mn^(4+) doped phosphors show promising prospect in commercial application to effectively expand color gamut of phosphor converted LED displays. Here, we report a type of Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) phosphors with regular cage-like micro-spherical morphologies. The micron size spherical precursors were synthesized with a propylene oxide (PO) driven fast sol–gel method. The cage -like spherical morphology is beneficial to efficiently trapping much incident light to enhance the PL of the phosphors. Being calcined at 1300 ℃, Sr_(2)MgAl_(21.978)O_(36):0.022Mn^(4+) only exhibits the internal quantum efficiency (IQE) of 24.91%. With the Mg^(2+)-Mn^(4+) codoping and Y^(3+)/Sr^(2+) substituting strategies, to fulfill charge balance and produce John-Teller distortion, IQE of Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) can be further improved up to 36.45%. The CIE color coordinates of Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) under near ultraviolet excitation can be stably fixed to (0.723, 0.227) at deep red region. It thus finds a potential application as pc-LED display with much broader color gamut than that of the NTSC standard. Therefore, Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) micron size spheres can be employed as promising red phosphors for high performance LED displays.展开更多
The 2019 novel coronavirus disease(COVID-19)outbreak is a global crisis that has placed small and medium enterprises(SMEs)under huge pressure to survive,requiring them to respond effectively to the crisis.SMEs have ad...The 2019 novel coronavirus disease(COVID-19)outbreak is a global crisis that has placed small and medium enterprises(SMEs)under huge pressure to survive,requiring them to respond effectively to the crisis.SMEs have adopted various digital tech no logies to cope with this crisis.Using a data set from a survey with 518 Chin ese SMEs,the study examines the relati on ship between SMEs'digitalizatio n and their public crisis responses.The empirical results show that digitalization has enabled SMEs to respond effectively to the public crisis by making use of their dynamic capabilities.In addition,digitalization can help improve SMEs'performance.We propose a theoretical framework ofdigitalization and crisis respohses for SMEs and present three avenues for future research.展开更多
To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance,yet limited success has been achieved.Here,via s...To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance,yet limited success has been achieved.Here,via simple melting-quenching and subsequent thermal activation,we report the successful preparation of transparent nano-structured glass-ceramics embedded in Sr2Lu F7 nano-crystals(~26 nm),as evidenced by X-ray diffraction,transmission electron microscopy(TEM),and high resolution TEM.The successful incorporation of dopants into formed Sr2Lu F7 nano-crystals with low phonon energy results in highly tunable blue–green photoemission,which depends on excitation wavelength,dopant type,and temperature.We found that Eu3+and Eu2+ions co-exist in this hybrid optical material,accompanied by the broadband blue emission of Eu2+and sharp red emissions of Eu3+.A series of optical characterizations are summoned,including emission/excitation spectrum and decay curve measurement,to reveal the reduction mechanism of Eu3+to Eu2+.Furthermore,near green–white photoemission is achieved via the enrichment of Tb3+/Eu3+into crystallized Sr2Lu F7 nano-crystals.The temperature-dependent visible photoemission reveals thermal activation energy increases with the precipitation of Sr2Lu F7 nano-crystals in a glass matrix,suggesting better thermal stability of glass-ceramics than precursor glasses.These results could not only deepen the understanding of glass-ceramics but also indicate the promising potential of Eu3+/Tb3+-ions-doped Sr2Lu F7 glass-ceramics for UV pumped white light emitting diodes(WLEDs)with good thermal stability.展开更多
基金This work was supported by the Department of Education of Zhejiang Province （No.20060496） and the Natural Science Foundation of Zhejiang Province （No.Y406309）.
文摘Er^3＋ doped SrTiO3 ultrafine powders were prepared by solid state reaction in a molten NaCl flux. The structural properties were characterized by X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. The Stokes emission spectra of Er^3＋ in SrTiO3：Er^3＋ ranging from green to near infrared region were investigated under 514.5 nm laser excitation. The green and red upconverted luminescence spectra of Er^3＋ were measured under excitation into the 419/2 level by 785 nm laser. The upconversion mechanisms were studied in detail through laser power dependence and Er^3＋ ion concentration dependence of upconverted emissions, and results show that excited state absorption and energy transfer process are the possible mechanisms for the upconversion. The upconversion properties indicate that SrTiO3：Er^3＋ may be used in upconversion phosphors.
文摘Syndrome differentiation-based treatment is one of the key characteristics of Traditional Chinese Medicine(TCM).The process of syndrome differentiation is difficult and challenging due to its complexity,diversity and vagueness.Analyzing syndrome principles from historical records of TCM using data mining(DM)technology has been of high interest in recent years.Nevertheless,in most relevant studies,existing DM algorithms have been simply developed for TCM mining,while the combination of TCM theories or its characteristics with DM algorithms has rarely been reported.This paper presents a novel Symptom-Syndrome Topic Model(SSTM),which is a supervised probabilistic topic model with three-tier Bayesian structure.In the SSTM,syndromes are considered as observed topic labels to distinguish certain symptoms from possible symptoms according to their different positions.The generation of our model is in full compliance with the syndrome differentiation theory of TCM.Experimental results show that the SSTM is more effective than other models for syndrome differentiating.
文摘[ Objective ] This study aimed to optimize the extraction technology for rice bran oil. [ Method ] Using rice bran as raw material, effects of ultrasonicassisted extraction technology and different organic solvents, extraction durations, solid-liquid ratios and extraction temperatures on extraction results of rice bran oil were investigated. Based on the results of single-factor experiment, L9 （34 ） orthngonal experiment with three factors at three levels was conducted to optimize the extraction technological parameters, thus obtaining the optimal technological conditions for extracting rice bran oil. [ Result] Anhydrous ethanol led to the best extraction result; after ultrasonic treatment, the extraction rate of rice bran oil from raw material was not enhanced. The optimized technological parameters were ： extraction temperature of 80 ℃, extraction duration of 20 rain and solid-liquid ratio of 1：24 （ g： ml）. Under the optimized technological conditions, the extraction rate of rice bran oil reached 19.33%. [ Conclusion] This study laid solid foundation for further investigation and development of rice bran oil.
基金supported by the National Natural Science Foundation of China (No. 40821003)the Guangdong Natural Science Foundation (No. 7118013)the State Key Laboratory of Organic Geochemistry and the Hong Kong Polytechnic University Joint Student Program
文摘Air samples were collected simultaneously at platform,mezzanine and outdoor in five typical stations of subway system in Shanghai,China using stainless steel canisters and analyzed by gas chromatography-mass selective detector （GC-MSD） after cryogenic pre-concentration.Benzene,toluene,ethylbenzene and xylenes （BTEX） at the platforms and mezzanines inside the stations averaged （10.3±2.1）,（38.7±9.0）,（19.4±10.1） and （30.0±11.1） μg/m 3,respectively;while trichloroethylene （TrCE）,tetrachloroethylene （TeCE） and para-dichlorobenzene （pDCB）,vinyl chloride and carbon tetrachloride were the most abundant chlorinated hydrocarbons inside the stations with average levels of （3.6±1.3）,（1.3±0.5）,（4.1±1.1）,（2.2±1.1） and （1.2±0.3） μg/m 3,respectively.Mean levels of major aromatic and chlorinated hydrocarbons were higher indoor （platforms and mezzanines） than outdoor with average indoor/outdoor （I/O） ratios of 1.1–9.5,whereas no significant indoor/outdoor differences were found except for benzene and TrCE.The highly significant mutual correlations （p0.01） for BTEX between indoor and outdoor and their significant correlation （p0.05） with methyl tert-butyl ether （MTBE）,a marker of traffic-related emission without other indoor and outdoor sources,indicated that BTEX were introduced into the subway stations from indoor/outdoor air exchange and traffic emission should be their dominant source.TrCE and pDCB were mainly from indoor emission and TeCE might have both indoor emission sources and contribution from outdoor air,especially in the mezzanines.
基金supported by the National Natural Science Foundation of China (11974315)。
文摘Dual-excitation and dual-emission Y_(4)GeO_(8):Bi^(3+),Sm^(3+)phosphors were manufactured by traditional solidphase sintering technique.The X-ray diffraction,morphology,photoluminescence,energy transfer process and temperature sensing properties of Y_(4)GeO_(8):Bi^(3+),Sm^(3+)samples were comprehensively evaluated.The Y4GeO_(8):Bi^(3+),Sm^(3+)phosphors exhibit characteristic emissions of Bi^(3+)(^(3)P_(1)→^(1)S_(0)) and Sm^(3+)(^(4)G_(5/2)→^(6)H)under both 290 and 347 nm excitations.In fluorescence intensity ratio and Commission International de L'Eclairage coordinates modes,Y_(4)GeO_(8):Bi^(3+),Sm^(3+)samples present excellent temperature measurement performance.The maximum relative sensitivity(S_(r-max)) values of the former are 1.55%/K(460 K,290 nm excitation) and 0.82%/K(506 K,347 nm excitation).The S_(r-max)(x) values of the latter are 0.21 %/K(437 K,290 nm excitation) and 0.15%/K(513 K,347 nm excitation).These results illustrate that Y_(4)GeO_(8):Bi^(3+),Sm^(3+)phospho rs can be used as a candidate material for a dual-mode optical thermometer under dual-excitation.
基金Project supported by the Natural Science Foundation of Zhejiang Province (LY21A040005)the National Natural Science Foundation of China (11804303,11974315,51802285)。
文摘In this work,a group of Bi^(3+)/Eu^(3+)-doped SiO2-Al_(2)O_(3)-MCO_(3)(M=Ca,Sr,Ba) glasses were fabricated through melt-quenching method.Their structure and photoluminescence characters were studied via Xray diffraction(XRD),UV-Vis transmission spectra(TRS),excitation spectra,emission spectra and decay lifetimes.The XRD results show that no nano-crystal phase forms in glass matrix with different doping concentrations of Bi^(3+)and Eu^(3+)ions.Through regulating optical alkalinity value,the intensity of Bi^(3+)ions increases and the peak position shifts to red wavelength.The Bi^(3+)/Eu^(3+) co-doped glasses show a blue-white-yellow-red luminescence by changing concentration of Eu^(3+) ions.Energy transfer efficiency from Bi^(3+) to Eu^(3+) can reach as high as 10.54%.At 423 K, the emission intensity of 55SiO_(2)-10Al_(2)O_(3)-35BaO-0.25Bi_(2)O_(3)(GBE0.5) is 31.1% of that at 308 K.Meanwhile,the activation energy of the glass matrix is 0.251 eV.All results suggest that these Bi^(3+)/Eu^(3+) co-doped glass samples possess potential application in LED field.
基金Research Grants Council(RGC)of the Government of the Hong Kong Special Administrative Region(PolyU 152124/21 E and N_PolyU530/20)research support scheme of Research Institute for Land and Space at The Hong Kong Polytechnic University(1-CD79)Start-up Fund for RAPs under the Strategic Hiring Scheme of the Hong Kong Polytechnic University(1-BD3T).
文摘Ozone(O_(3))pollution is usually linked to warm weather and strong solar radiation,making it uncommon in cold winters.However,an unusual occurrence of four high O_(3)episode days(with maximum hourly concentrations exceeding 100 ppbv and peaking at 121 ppbv)was recorded in January 2018 in Lanzhou city,China.During these episodes,the average daytime concentration of total non-methane volatile organic compounds(TVOCs)reached 153.4±19.0 ppbv,with alkenes—largely emitted from the local petrochemical industry—comprising 82.3±13.1 ppbv.Here we show a photochemical box model coupled with a Master Chemical Mechanism to elucidate the mechanisms behind this unusual wintertime O_(3)pollution.We find that the typically low temperatures(−1.7±1.3℃)and weak solar radiation(263.6±60.7 W m^(-2))of those winter episode days had a minimal effect on the reactivity of VOCs with OH radicals.Instead,the ozonolysis of alkenes generated Criegee intermediates,which rapidly decomposed into substantial ROx radicals(OH,HO_(2),and RO_(2))without sunlight.This radical production led to the oxidation of VOCs,with alkene ozonolysis ultimately contributing to 89.6±8.7%of the O_(3)formation during these episodes.This mechanism did not activate at night due to the depletion of O_(3)by the NO titration effect.Furthermore,the findings indicate that a reduction of alkenes by 28.6%or NO_(x)by 27.7%in the early afternoon could significantly mitigate wintertime O_(3)pollution.Overall,this study unravels the unique mechanism of alkene-induced winter O_(3)pollution and offers a reference for winter O_(3)reduction strategies in the petrochemical industrial regions.
基金supported by the National Key Research and Development Program of China(Grant No:2022YFC3703505)the Research Funds for the Frontiers Science Center for Critical Earth Material Cycling,Nanjing University(Grant No:090414380031).
文摘Land-sea atmosphere interaction(LSAI)is one of the important processes affecting ozone(O_(3))pollution in coastal areas.The effects of small-scale LSAIs like sea-land breezes have been widely studied.However,it is not fully clear how and to what extent the large-scale LSAIs affect O_(3) pollution.Here we explored an O_(3) episode to illuminate the role of large-scale LSAIs in O_(3) pollution over the BohaieYellow Seas and adjacent areas through observations and model simulations.The results show that the northern Bohai Sea's coastal region,influenced by the Mongolian High,initially experienced a typical unimodal diurnal O_(3) variation for three days,when O_(3) precursors from BeijingeTianjineHebei,Shandong,and Northeast China were transported to the BohaieYellow Seas.Photochemical reactions generated O_(3) within marine air masses,causing higher O_(3) levels over the seas than coastal regions.As the Mongolian High shifted eastward and expanded,southerly winds on its western edge transported O_(3)-rich marine air masses toward the coast,prolonging pollution for an additional three days and weakening diurnal variations.Subsequently,emissions from the Korean Peninsula and marine shipping significantly affected O_(3) levels in the northern Bohai Sea(10.7%and 13.7%,respectively).Notably,Shandong's emissions played a substantial role in both phases(27.5%and 26.1%,respectively).These findings underscore the substantial impact of large-scale LSAIs driven by the Mongolian High on O_(3) formation and pollution duration in coastal cities.This insight helps understand and manage O_(3) pollution in northern Bohai Sea cities and broadly applies to temperate coastal cities worldwide.
基金This work has been commissioned by the UKRI(EPSRC,NERC,AHRC)funded by RECLAIM Network Plus project(EP/W034034/1,EP/W033984)under its synthesis review seriesThe following authors acknowledge the funding received through their grants:P.K.and L.J.(NE/X002799/1,NE/X002772/1),L.J.(H2020 REGREEN,EU Grant agreement No.821016,2021YFE93100),G.M.L.(FAPESP 2019/08783-0),C.D.F.R.(EP/R017727),L.M.(ARC Grant No.IC220100012),H.G.(RGC Grant No.C5024-21G),M.F.A.and E.D.F.(FAPESP Grant No.2016/18438-0,2022/02365-5),S.J.C.(NSFC Grant No.52225005),R.Y.(NSFC Grant No.52278090),F.W.(NKP Grant No.2020YFC180700),J.E.(NE/X000443/1),and F.C.(NE/M010961/1,NE/V002171/1).The authors thank Andrea Sofia Majjul Fajardo for her contribution to the initial design of certain figures.We also thank the team members of GCARE and its Guildford Living Lab(GLL),as well as the participants in the RECLAIM Network Plus Horizon Scanning Workshop.
文摘The combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change.Yet,the risk of urban overheating can be mitigated by urban green-blue-grey infrastructure(GBGI),such as parks,wetlands,and engineered greening,which have the potential to effectively reduce summer air temperatures.Despite many reviews,the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear.This systematic literature review synthesizes the evidence base for heat mitigation and related co-benefits,identifies knowledge gaps,and proposes recommendations for their implementation to maximize their benefits.After screening 27,486 papers,202 were reviewed,based on 51 GBGI types categorized under 10 main divisions.Certain GBGI(green walls,parks,street trees)have been well researched for their urban cooling capabilities.However,several other GBGI have received negligible(zoological garden,golf course,estuary)or minimal(private garden,allotment)attention.The most efficient air cooling was observed in botanical gardens(5.0±3.5℃),wetlands(4.9±3.2℃),green walls(4.1±4.2℃),street trees(3.8±3.1℃),and vegetated balconies(3.8±2.7℃).Under changing climate conditions(2070–2100)with consideration of RCP8.5,there is a shift in climate subtypes,either within the same climate zone(e.g.,Dfa to Dfb and Cfb to Cfa)or across other climate zones(e.g.,Dfb[continental warm-summer humid]to BSk[dry,cold semi-arid]and Cwa[temperate]to Am[tropical]).These shifts may result in lower efficiency for the current GBGI in the future.Given the importance of multiple services,it is crucial to balance their functionality,cooling performance,and other related co-benefits when planning for the future GBGI.This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritizing effective interventions to reduce the risk of urban overheating,filling research gaps,and promoting community resilience.
基金supported by the National Key R&D Program of China(Nos.2017YFC0212802 and 2017YFC0212004)the support of MOST project(No.2017YFC0212001)for the collaboration。
文摘We present the continuously measurements of volatile organic compounds(VOCs)at a receptor site(Wan Qing Sha,WQS)in the Pearl River Delta(PRD)region from September to November of 2017.The average mixing ratios of total VOCs(TVOCs)was 36.3±27.9 ppbv with the dominant contribution from alkanes(55.5%),followed by aromatics(33.3%).The diurnal variation of TVOCs showed a strong photochemical consumption during daytime,resulting in the formation of ozone(O_(3)).Five VOC sources were resolved by the positive matrix factorization(PMF)model,including solvent usage(28.6%),liquid petroleum gas(LPG)usage(24.4%),vehicle exhaust(21.0%),industrial emissions(13.2%)and gasoline evaporation(12.9%).The regional transport air masses from the upwind cities of south China can result in the elevated concentrations of TVOCs.Low ratios of TVOCs/NO_(x)(1.53±0.88)suggested that the O_(3) formation regime at WQS site was VOC-limited,which also confirmed by a photochemical box model with the master chemical mechanism(PBM-MCM).Furthermore,the observation on high-O_(3) episode days revealed that frequent O_(3) outbreaks at WQS were mainly caused by the regional transport of anthropogenic VOCs especially for aromatics and the subsequent photochemical reactions.This study provides valuable information for policymakers to propose the effective control strategies on photochemical pollution in a regional perspective.
基金Project supported by National Natural Science Foundation of China(11974315)Guangdong Science and Technology Innovation Strategy Foundation of China(20190310)。
文摘Herein,we reported novel Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors elaborated via conventional solid-state reaction.and we further explored their properties as optical thermometer by using fluorescence intensity ratio(FIR)method complemented by detailed analysis on crystal structure,up-conversion luminescence and energy transfer from Yb^(3+)to Er^(3+).Upon 980 nm laser excitation,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors present525,547 and 659 nm emission bands assigned to the characteristic transitions of Er^(3+).Furthermore,Y_(4)GeO_(8):Er^(3+),Yb^(3+)samples show outstanding temperature sensing performances.To be specific,the minimal temperature resolution is 0.03 K(303 K),and the relative sensitivity of FIR can be up to 1.152%/K(303 K).Hence,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors can be possible candidates for thermometry devices.
基金Project(No.GREKF09-08)supported by the State Key Laboratory of Genetic Resources and Evolution,Kunming Institute of Zoology,Chinese Academy of Sciences,China
文摘Objective:There are many reports on associations between spermatogenesis and partial azoospermia factor c(AZFc) deletions as well as duplications;however,results are conflicting,possibly due to differences in methodology and ethnic background.The purpose of this study is to investigate the association of AZFc polymorphisms and male infertility in the Yi ethnic population,residents within Yunnan Province,ChinaMethods:A total of 224 infertile patients and 153 fertile subjects were selected in the Yi ethnic population.The study was performed by sequence-tagged site plus/minus(STS+/) analysis followed by gene dosage and gene copy definition analysis.Y haplotypes of 215 cases and 115 controls were defined by 12 binary markers using single nucleotide polymorphism on Y chromosome(Y-SNP) multiplex assays based on single base primer extension technology.Results:The distribution of Y haplotypes was not significantly different between the case and control groups.The frequencies of both gr/gr(7.6% vs.8.5%) and b2/b3(6.3% vs.8.5%) deletions do not show significant differences.Similarly,single nucleotide variant(SNV) analysis shows no significant difference of gene copy definition between the cases and controls.However,the frequency of partial duplications in the infertile group(4.0%) is significantly higher than that in the control group(0.7%).Further,we found a case with sY1206 deletion which had two CDY1 copies but removed half of DAZ genes.Conclusions:Our results show that male infertility is associated with partial AZFc duplications,but neither gr/gr nor b2/b3 deletions,suggesting that partial AZFc duplications rather than deletions are risk factors for male infertility in Chinese-Yi population.
基金Project supported by the National Natural Science Foundation of China(11974315,51802285)the Natural Science Foundation of Zhejiang Province(LZ20E020002)。
文摘Single-phase Y_(2)BaAl_(4)SiO_(12):Tb^(3+),Eu^(3+)phosphors with adjustable luminescence were successfully prepared by high-temperature solid-state reaction method.The structural,luminescent properties and ene rgy transfer(ET) process of Y_(2)BaAl_(4)SiO_(12):Tb^(^(3+)),Eu^(3+)phosphors were syste matically analyzed with the help of X-ray diffraction(XRD),scanning electron microscopy(SEM),excitation spectra,emission spectra and photoluminescence decay curves.Tunable luminescence ranging from green through yellow and definitively to red can be achieved by elevating amounts of Eu^(3+)ions in Tb^(3+),Eu^(3+)co-doped samples.Besides,the ET mechanism and efficiency were also analyzed and the maximum ET efficiency is 67%.All the results show that Y_(2)BaAl_(4)SiO_(12):Tb^(3+),Eu^(3+)phosphors can be used in solid-state lighting.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China （No. LYI5E050003）, the National Natural Science Foundation of China （No. 51675470）, and the Fundamental Research Funds for the Central Universities, China （No. 2015QNA4003）
文摘The multi-pass scheduling method is a key issue in die-less spinning for determining the quality of the final products, including their shape deviations and wall thicknesses, and has drawn increasing interest in recent studies devoted to trying to improve the accuracy of the formed parts. In this paper, two main parameters, roller path profiles and deformation allocations in each pass, are considered in newly proposed multi-pass scheduling and optimizing methods in die-less spinning. Four processing methods with different roller path profiles and with three deformation allocation methods are proposed for investigating the influence of scheduling parameters on product qualities. The ＇similar geometry principle for restraining shape deviation＇ and the ＇small curvature principle for maintaining wall thickness＇ are presented for optimal design of roller path profiles; in addition, the ＇uniform allocation principle for maintaining wall thickness＇ and the ＇large deformation principle for restraining shape deviation＇ are brought forward as suggestions for deformation allocations. Based on these principles, a scheduling method denoted by RF＋（FP ＆ EHS） is presented to improve the comprehensive quality of a product of die-less spinning.
文摘Layered carbon materials(LCMs)are composed of basic carbon layer units,such as graphite,soft carbon,hard carbon,and graphene.While they have been widely applied in the anode of potassium-ion batteries,the potassium storage mechanisms and performances of various LCMs are isolated and difficult to relate to each other.More importantly,there is a lack of a systematic understanding of the correlation between the basic microstructural unit(crystallinity and defects)and the potas-sium storage behavior.In this review,we explored the key structural factors affecting the potassium storage in LCMs,namely,the crystallinity and defects of carbon layers,and the key parameters(L_(a),L_(c),d_(002),I_(D)/I_(G))that characterize the crystallinity and defects of different carbon materials were extracted from various databases and literature sources.A structure–property database of LCMs was thus built,and the effects of these key structural parameters on the potassium storage properties,including the capacity,the rate and the working voltage plateau,were systematically analyzed.Based on the structure–prop-erty database analysis and the guidance of thermodynamics and kinetics,a relationship between various LCMs and potas-sium storage properties was established.Finally,with the help of machine learning,the key structural parameters of layered carbon anodes were used for the first time to predict the potassium storage performance so that the large amount of research data in the database could more effectively guide the scientific research and engineering application of LCMs in the future.
基金Project supported by the National Natural Science Foundation of China (51872255,51672243)。
文摘With narrow red photoluminescence (PL) bands, tetravalent Mn^(4+) doped phosphors show promising prospect in commercial application to effectively expand color gamut of phosphor converted LED displays. Here, we report a type of Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) phosphors with regular cage-like micro-spherical morphologies. The micron size spherical precursors were synthesized with a propylene oxide (PO) driven fast sol–gel method. The cage -like spherical morphology is beneficial to efficiently trapping much incident light to enhance the PL of the phosphors. Being calcined at 1300 ℃, Sr_(2)MgAl_(21.978)O_(36):0.022Mn^(4+) only exhibits the internal quantum efficiency (IQE) of 24.91%. With the Mg^(2+)-Mn^(4+) codoping and Y^(3+)/Sr^(2+) substituting strategies, to fulfill charge balance and produce John-Teller distortion, IQE of Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) can be further improved up to 36.45%. The CIE color coordinates of Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) under near ultraviolet excitation can be stably fixed to (0.723, 0.227) at deep red region. It thus finds a potential application as pc-LED display with much broader color gamut than that of the NTSC standard. Therefore, Sr_(2-z)Mg_(1+y)Y_(z)Al_(22-x)O_(36):xMn^(4+) micron size spheres can be employed as promising red phosphors for high performance LED displays.
基金supported by the National Natural Science Foundation of China under Grant 71872178。
文摘The 2019 novel coronavirus disease(COVID-19)outbreak is a global crisis that has placed small and medium enterprises(SMEs)under huge pressure to survive,requiring them to respond effectively to the crisis.SMEs have adopted various digital tech no logies to cope with this crisis.Using a data set from a survey with 518 Chin ese SMEs,the study examines the relati on ship between SMEs'digitalizatio n and their public crisis responses.The empirical results show that digitalization has enabled SMEs to respond effectively to the public crisis by making use of their dynamic capabilities.In addition,digitalization can help improve SMEs'performance.We propose a theoretical framework ofdigitalization and crisis respohses for SMEs and present three avenues for future research.
基金the National Natural Science Foundation of China(Nos.51902178,11804188,51702172,and 51802285)the Natural Science Foundation of Shandong Province(No.ZR201807060932)the Open Fund of the State Key Laboratory of Luminescent Materials and Devices(South China University of Technology)(No.2019-skllmd-15)。
文摘To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance,yet limited success has been achieved.Here,via simple melting-quenching and subsequent thermal activation,we report the successful preparation of transparent nano-structured glass-ceramics embedded in Sr2Lu F7 nano-crystals(~26 nm),as evidenced by X-ray diffraction,transmission electron microscopy(TEM),and high resolution TEM.The successful incorporation of dopants into formed Sr2Lu F7 nano-crystals with low phonon energy results in highly tunable blue–green photoemission,which depends on excitation wavelength,dopant type,and temperature.We found that Eu3+and Eu2+ions co-exist in this hybrid optical material,accompanied by the broadband blue emission of Eu2+and sharp red emissions of Eu3+.A series of optical characterizations are summoned,including emission/excitation spectrum and decay curve measurement,to reveal the reduction mechanism of Eu3+to Eu2+.Furthermore,near green–white photoemission is achieved via the enrichment of Tb3+/Eu3+into crystallized Sr2Lu F7 nano-crystals.The temperature-dependent visible photoemission reveals thermal activation energy increases with the precipitation of Sr2Lu F7 nano-crystals in a glass matrix,suggesting better thermal stability of glass-ceramics than precursor glasses.These results could not only deepen the understanding of glass-ceramics but also indicate the promising potential of Eu3+/Tb3+-ions-doped Sr2Lu F7 glass-ceramics for UV pumped white light emitting diodes(WLEDs)with good thermal stability.
