【作者】 郑薇；

【导师】 王锐；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2022， 博士

【摘要】 稀土掺杂上转换发光材料因其窄的发射波段、长的荧光寿命、小的背景干扰及可调的输出光色等优势,现已在数据储存、生物成像、3D显示、防伪和温度探测等诸多领域得到了广泛应用。然而低的发光效率、差的温度探测灵敏性以及窄的光色调节范围仍然严重阻碍了上转换发光材料的实际应用。本论文以具有较好的化学稳定性和物理稳定性的稀土掺杂氧化钆为研究对象,针对发光强度低和温度探测灵敏度差的问题,利用便捷的激光敏化处理增强Yb/Er/Gd₂O₃上转换荧光强度及温度探测灵敏度,实现高效率、高温度探测灵敏性上转换荧光材料的构筑;另外针对于目前存在的光色调节问题,在Yb/Er/Gd₂O₃体系引入Tm³⁺,利用激光功率调控稀土离子间的能量传递和交叉驰豫,在稀土掺杂氧化钆单体内实现便捷可调的全光色输出。通过对上转换纳米材料的微观形貌调控,解决热处理过程中颗粒团聚问题,增强了上转换发光强度。采用水热法和共沉淀法及相应的热处理过程制备不同形貌的Yb/Er/Gd₂O₃纳米粒子,探究热处理过程中样品的形貌的变化,研究发现利用共沉淀法及热处理过程制备的球形Yb/Er/Gd₂O₃纳米粒子,退火处理后很好地维持了前驱体的形貌,且实现较强的上转换荧光输出。而后优化了稀土离子浓度,很好地避免了稀土离子间的浓度淬灭,确定了最佳的Er³⁺离子掺杂浓度为1%mol,最佳的Yb³⁺离子掺杂浓度为10 mol%。通过激光敏化调控Yb/Er/Gd₂O₃纳米材料局部结构,实现高效率多光色上转换荧光输出。在Yb/Er/Gd₂O₃体系中,利用激光热效应产生局部热点,增强荧光强度和扩大光色调节范围。当激光功率为1511 m W,粒径尺寸为309 nm,测试功率为534 m W,Yb/Er/Gd₂O₃纳米晶的上转换红光强度及绿光强度分别提高913倍及894倍。通过一系列结构测试、光谱测试及动力学分析确定了激光敏化上转换荧光增强是主要是利用样品局部形貌和结构变化增加敏化剂向激活剂的能量传递实现的。构建热激活上转换发光体系,抑制高温环境下的荧光淬灭,增强温度探测的准确性及灵敏度。研究了激光处理前后Yb/Er/Gd₂O₃样品发光性能随温度的变化关系。研究发现,未经激光处理的Yb/Er/Gd₂O₃样品呈现的是传统的热淬灭发光,而当样品经过激光敏化后,在一定温度范围内,随着温度的提升,样品的荧光强度不断地增强,实现了热激活上转换发光。此外,探究了激光处理前后Yb/Er/Gd₂O₃样品基于Er³⁺离子的不同类型能级对的温度传感性能,实验结果表明,激光敏化处理后Yb/Er/Gd₂O₃粒子的相对灵敏度得到了大幅度提高。在578 K的测试温度下,基于Er³⁺非温度耦合能级对的相对灵敏度值高达4.5%K^-1,远高于原样品的相对灵敏度值。通过调控稀土离子间非稳态能量传递和交叉驰豫,在Yb/Er/Tm/Gd₂O₃单体内实现可控全光色输出。尽管Yb/Er/Gd₂O₃体系具有良好的光色调节性能,但其光色调节范围限制于红光到绿光区的转变。基于此引入具有蓝光输出的Tm³⁺,利用激光敏化和功率调节,在Yb/Er/Tm/Gd₂O₃单体内实现了高纯度的白光输出及全光色可调上转换荧光输出。此外,探究了激光敏化光色调控对不同稀土离子浓度掺杂单体的适用性,研究结果表明,当Er³⁺浓度范围在0.1-1.5 mol%,Tm³⁺浓度范围在0.3-1.0 mol%,通过激光敏化功率和测试功率调节,Yb/Er/Tm/Gd₂O₃样品均可实现明亮的白光输出及宽色域的光色调控。最后利用激光敏化多色光输出特性构筑具有不同荧光光色的图案,实现了防伪标识,为上转换发光材料的防伪应用奠定了基础。更多还原

【Abstract】 Lanthanide ions doped upconversion fluorescence materials（LUFM）have achieved extensive applications,spanning from data storage,biological imaging,3D displays to solar energy,anticounterfeiting and temperature detection owning to their unique properties such as sharp-band emitting,long fluorescence decay times,low background interference as well as controllable luminescent color.Unfortunately,low luminescent efficiency,poor sensitivity of temperature detection as well as narrow color adjustment range still seriously hinder the application of LUFM.Here,lanthanide doped gadolinium oxide with good physical and chemical stability was researched.The convenient laser sensitization treatment was utilized to enhance the luminescent intensity as well as temperature sensitivity of Yb/Er/Gd₂O₃sample.In addition,the bright white emission and adjustable full-color emission were realized by controlling the energy transfer and cross relaxation process via tuning laser power.Particle agglomeration during heat treatment was studied and the upconversion luminescence intensity was improved by adjusting the morphology of Yb/Er/Gd₂O₃upconversion nanomaterials.Yb/Er/Gd₂O₃upconversion nanoparticles were synthesized through hydrothermal method and coprecipitation method following thermal treatment,and the influence of thermal treatment on morphology was studied.Results indicated that the nanospheres morphology via coprecipitation method well maintained after thermal treatment,and strong upconversion emission was also achieved in Yb/Er/Gd₂O₃nanospheres.Then the content of lanthanide ions was optimized,the concentration quenching between lanthanide ions was effectively avoided,and the content of Er³⁺and Yb³⁺were determined to be as 1%mol and 10 mol%,respectively.High efficiency multi-color upconversion fluorescence was achieved via adjusting the local structure of Yb/Er/Gd₂O₃nanoparticles induced by laser sensitization.In Yb/Er/Gd₂O₃system,local hot spots were generated by laser thermal effect,leading to the enhancement of fluorescence intensity and the expand of color adjustment range.As the laser sensitized power was 1511 m W,the nanospheres size was 309 nm,and the test power was 534 m W,913-fold and 894-fold improvement were realized in terms of the red and green emitting intensity.Structured characterization,spectrum tests and lifetime tests show that the laser-sensitized upconversion emission improvement is due to the increase of energy transfer from Yb³⁺to Er³⁺.Thermally activated upconversion luminescence was constructed to inhibit fluorescence quenching at high temperature and enhance the accuracy and sensitivity of temperature detection.The temperature-dependent luminescence and temperature sensing performance of Yb/Er/Gd₂O₃particles before and after laser treatment were explored.It is found that the Yb/Er/Gd₂O₃sample without laser treatment presented the regular thermal quenching luminescence.In contrast,the laser treated sample showed thermal activated upconversion luminescence,which overcomed the limitation of the regular thermal quenching luminescence temperature detection.In addition,the relative sensitivity of the laser sensitized sample was as high as 4.5%K^-1at 578 K,which was significantly improved compared with Yb/Er/Gd₂O₃particles without laser treatment.Full color upconversion luminescence was realized by regulating the unsteady cross relaxation and energy transfer between rare earth ions.Although tunable color emission was achieved in Yb/Er/Gd₂O₃system,the color regulation range was limited.On basis of this,Tm³⁺with blue light output was introduced in Yb/Er/Gd₂O₃system.By regulating the power,bright white light output and tunable full color upconversion emission were realized in Yb/Er/Tm/Gd₂O₃sample.The relationship between lanthanide ions content and laser sensitized color adjustment were explored.Experimental results indicated that Yb/Er/Tm/Gd₂O₃crystals could realize bright white light emitting as well as wide range of color tune by changing the laser sensitization power and test power in a certain doping range,overcoming the shortcoming of conventional concentration-dependent color adjustment.In addition,the anti-counterfeiting identification was realized through manufacturing different patterns,which lays a foundation for the anti-counterfeiting application of upconversion luminescence materials.更多还原