脂质体封端CsPbX3(X=Cl,Br,I)纳米晶体的制备及在发光二极管中的应用

以脂质体充当表面封端配体修饰合成后的CsPbX₃纳米晶体.封端CsPbX₃纳米晶能保持原始形状和粒径大小,相对量子产率提升至（100±3）%,发射光谱在411~626 nm范围内可调.将其存储于空气（温度25℃,相对湿度50%）中150 d仍保持立方晶型.以DOPC-CsPbBr₃为颜色转换器可制造显色指数高达91.2的白色发光二极管,应用前景广阔.     

Near UV luminescent Cs2NaBi0.75Sb0.25Cl6 perovskite colloidal nanocrystals with high stability

Near UV highly luminescent colloidal Cs₂NaBiCl₆ nanocrystals（NCs） were synthesized by a simple lowcost ligand-assisted reprecipitation method. In our strategy, metal chloride precursors were added to the mixture of anti-solvent and ligand at room-temperature. The obtained Cs₂NaBiCl₆ NCs exhibited a bright blue emission with significantly improved photoluminescence quantum yield（PLQY） of 39.05%. The optical properties and stability were greatly enhanced...     

醋酸铅作为铅源合成CH3NH3PbBr3-xClx纳米晶体颗粒

Lead acetate, which is highly soluble in dimethylformamide, was used to synthesize mixed halide perovskite CH₃NH₃PbBr_3-xCl_x (MA = CH₃NH₃, 0 ≤ x ≤ 3) nanocrystals (NCs). This method provides an approach to address the low solubility of lead halides, especially lead chloride. Different Br/Cl ratios in MAPbBr_3-xCl_x lead to various optical properties. The photoluminescence emission peak can be tuned from 399 to 527 nm. Their full-widths at half-maxima (FWHM) are about 20 nm. MAPbBr_3-xCl_x NCs have an average diameter of ~(11 ± 3) nm and have uniform dispersion in toluene. The MAPbBr₃ NCs have a long average recombination lifetime (τ_ave = 97.4 ns) and a photoluminescence quantum yield (PLQY) of up to 73%.     

SCN掺杂提高CsPbI3胶体量子点的稳定性和光探测性能

无机卤化物钙钛矿CsPbI₃胶体量子点因其优越的光电性能在光伏和发光器件领域中表现出极大的发展前景。然而,CsPbI₃较差的稳定性阻碍了实际应用。为此,我们采用SCN?离子掺杂CsPbI₃(SCN-CsPbI₃)量子点用于提高量子点的光学性能和稳定性。研究表明,SCN?离子掺杂不仅减少了量子点缺陷、改善了光学性能,还提高了Pb-X键能、量子点结晶质量以及钙钛矿结构稳定性。结果表明,SCN-CsPbI₃量子点的荧光量子产率(PLQY)超过90%,远高于未掺杂原始样品(PLQY为68%)。高的荧光量子产率表明量子点具有较低的缺陷态密度,这归咎于缺陷的减少。空间限制电荷和时间分辨荧光光谱等研究也证实SCN?离子掺杂减少了量子点的缺陷。此外,SCN-CsPbI₃量子点展现出很好的抗水性能,其荧光强度在水中浸泡4 h后依然保持85%的初始值。而未掺杂原始样品的荧光性能很快消失,这是因为水诱导其相变。基于SCN-CsPbI₃量子点的光电探测器表现出宽波域响应(400–700 nm),高的响应率(90 mA·W^?1)和超过1011 Jones的探测度,远高于未掺杂原始量子点探测器的性能(响应率为60 mA·W^?1和探测度为1010 Jones)。     

无机铅卤钙钛矿纳米晶的合成、性能及应用

无机铅卤钙钛矿CsPbX₃(X=Cl,Br,I)纳米晶因具有较高荧光量子效率(~90%)、发光波长覆盖整个可见光谱(400~700 nm)、半高宽相对较窄(12~42 nm)等诸多优点而备受关注,这些性能使之成为当前最具有潜在应用价值的发光材料之一。 因此,近年来对该类无机铅卤钙钛矿材料的报道越来越多。 本文主要介绍了无机铅卤钙钛矿发光材料的发展历程、结构、制备方法、生长机理及当前的主要应用领域等,最后概括了无机铅卤钙钛矿发光材料在当前研究背景下所面临的问题并展望了下一阶段的发展方向,为进一步提高其光学性能及开发新型高效的无机铅卤钙钛矿发光材料奠定基础。     

Completely Amine-Free Open-Atmospheric Synthesis of High-Quality Cesium Lead Bromide (CsPbBr3) Perovskite Nanocrystals

Cesium lead halide perovskite nanocrystals (NCs) CsPbX₃ (X=Cl, Br, and I) have been prominent materials in the last few years due to their high photoluminescence quantum yield (PLQY) for light-emitting diodes and other significant applications in photovoltaics and optoelectronics. In colloidal CsPbX₃ synthesis, the most commonly used ligands are oleic acid and oleylamine. The latter plays an important role in surface passivation but may also be responsible for poor colloidal stability as a result of facile proton exchange leading to the formation of labile oleylammonium halide, which pulls halide ions out of the NC surface. Herein, a facile, efficient, completely amine-free synthesis of cesium lead bromide perovskite nanocrystals using hydrobromic acid as halide source and tri-n-octylphosphane as ligand under open-atmospheric conditions is demonstrated. Hydrobromic acid serves as labile source of bromide ion, and thus this three-precursor approach (separate precursors for Cs, Pb, Br) gives more control than a conventional single-source precursor for Pb and Br (PbBr₂). The use of HBr paved the way to eliminate oleylamine, and thus the formation of labile oleylammonium halide can be completely excluded. Various Cs:Pb:Br molar ratios were studied and optimum conditions for making very stable CsPbBr₃ NCs with high PLQY were found. These completely amine-free CsPbBr₃ perovskite NCs synthesized under bromine-rich conditions exhibit good stability and durability for more than three months in the form of colloidal solutions and films, respectively. Furthermore, stable tunable emission across a wide spectral range through anion exchange was demonstrated. More importantly, this work reports open-atmosphere-stable CsPbBr₃ NCs films exhibiting strong PL, which can be further used for optoelectronic device applications.     

全无机卤化铅钙钛矿的结构、热力学稳定性和电子性质

有机-无机杂化卤化铅钙钛矿因具有独特的电子和光学特性,已经成为光电领域最有前途的材料。但是,有机-无机钙钛矿材料及器件稳定性差,限制了其实际应用。与杂化钙钛矿相比,全无机卤化物钙钛矿CsPbX₃(X=Cl,Br,I)显示出更强的热稳定性。全无机卤化物钙钛矿CsPbX₃具有多个晶型,在不同的温度下呈不同相结构。目前,关于CsPbX₃的结构和物理性质仍存在争议。本文我们针对三个晶相α-,β-和γ-CsPbX₃的结构,热力学稳定性和电子性质进行了全面的理论研究。第一性原理计算表明,从高温α相到低温β相,然后再到γ相的相变伴随着PbX₆八面体的畸变。零温形成能计算表明,γ相最稳定,这与实验中γ相为低温稳定相的结论一致。电子性质计算表明,所有CsPbX₃钙钛矿都表现出直接带隙性质,并且带隙值从α相到β相再到γ相逐渐增加。这是由于相变发生时,Pb-X成键强度逐渐减弱,使价带顶能量降低,进而带隙增加。在所有相中,α相结构中较强的Pb-X相互作用,导致了较强的带边色散,使其具有较小的载流子有效质量。     

Impact of Zn-doping on the composition,stability, luminescence properties of silica coated all-inorganic cesium lead bromide nanocrystals and their biocompatibility

Cesium lead halide (CsPbX₃: X = I, Br, Cl) nanocrystals (NCs) are believed to be potential candidates for bioimaging applications. However, their low structural stability against polar solvents remains as a major limitation. To improve the NCs stability and maintain high emission intensity, we synthesized silica coated Zn-doped core@shell perovskite NCs via modified ligand assisted reprecipitation (LARP) synthetic method under relatively high humid condition. We systemically varied the composition inside the perovskite structure and then studied their photophysical properties and stability. Interestingly, the Zn-doping amount controls the ratio of CsPbBr₃ to Cs₄PbBr₆ perovskites inside the core and also facilitates the growth of (OA)₂PbBr₄ shell, enables overall increase in NCs emission intensity and stability. We observed green color emission from these NCs in the spectral range of 494-506 nm with a maximum photoluminescence quantum yield (PLQY) up to 88%. The optimized Zn-doped NCs exhibited nearly four times better water stability compared to the bare NCs and retain emission properties for several months even in highly polar solvents. Finally, we performed biocompatibility test of the NCs generated on biological samples and hydroponics test in a gardenia leaf for their potential bioimaging applications.     

多色高发光效率CsPbX3(X=Cl,Br,I)钙钛矿量子点的制备及其在发光二极管中的应用

采用室温合成法制备出一系列具有高发光效率和多色发光的CsPbX₃钙钛矿量子点(PQDs),反应全过程快速简便,且通过调节不同的卤素组成(Cl,Br,I)可以实现CsPbX₃ PQD的多色发光。 通过表征证明,CsPbX₃ PQDs呈立方晶型,平均粒径约为10 nm,发射光谱覆盖可见光波长范围为410~630 nm,半峰宽14~38 nm,荧光量子产率10%~90%。 最后将CsPbX₃ PQDs应用于发光二极管(LED)器件的制备中,在恒定电压下工作时,能保持LED器件的发光颜色、强度和颜色坐标不变。     

Synthesis and green up-conversion fluorescence of colloidal La0.78Yb0.20Er0.02F3/SiO2 core/shell nanocrystals

Water-soluble PVP-stabilized hexagonal-phase La_0.78Yb_0.20Er_0.02F₃ nanocrystals (NCs) were synthesized by hydrothermal method. The NCs were coated with a very thin silica shell, and amino groups were introduced to the surface of silica shells by copolymerization of 3-aminopropyl(triethoxy)silane. The core/shell NCs can be dispersed in ethanol and water to form stable colloidal solution. The transmission electron microscopy (TEM), selected area electron diffraction (SAED), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the core/shell materials. In addition, the green up-conversion fluorescence mechanism of La_0.78Yb_0.20Er_0.02F₃/SiO₂ NCs was studied with a 980-nm diode laser as excitation source. The water solubility, small core/shell particles size, and well colloidal stability mean the green up-conversion fluorescence NCs have potential applications in bioassay.     

Efficient Thermally Activated Delayed Fluorescence from All-Inorganic Cesium Zirconium Halide Perovskite Nanocrystals

Thermally activated delayed fluorescence (TADF) is generally observed in solid-state organic molecules or metal-organic complexes. However, TADF in all-inorganic colloidal nanocrystals (NCs) is rare. Herein, we report the first colloidal synthesis of an air-stable all-inorganic lead-free Cs₂ZrCl₆ perovskite NCs. The Cs₂ZrCl₆ NCs exhibit long-lived triplet excited state (138.2 μs), and feature high photoluminescence (PL) quantum efficiency (QY=60.37 %) due to TADF mechanism. The emission color can be easily tuned from blue to green by synthesizing the mixed-halide Cs₂ZrBr_xCl_6−x (0≤x≤1.5) NCs. Femtosecond transient absorption and temperature dependent PL measurements are performed to clarify the emission mechanism. In addition, Bi³⁺ ions are successfully doped into Cs₂ZrCl₆ NCs, which further extends the PL properties. This work not only develops a new lead-free halide perovskite NCs for potential optoelectronic applications, but also offers unique strategies for developing new inorganic phosphors.     

Preparation of monodisperse CdTe nanocrystals-SiO2 microspheres without ligands exchange

Fluorescent CdTe-SiO₂ composite microspheres were prepared by a sol–gel method without the exchange of surface ligands for the first time. We loaded CdTe nanocrystals (NCs) into the matrix of silica microspheres during the formation of composite spheres. In contrast to CdTe NCs in aqueous solutions, CdTe NCs in the composite microspheres revealed better stability while their fluorescence properties were retained due to the confined effects of silica matrix. In addition, we also investigated the dependency of properties of these composite spheres on such important synthesis factors as pH value, concentration and stabilizers during experiment procedure in details.     

Inorganically functionalized PbS-CdS colloidal nanocrystals: integration into amorphous chalcogenide glass and luminescent properties

Inorganic semiconductor nanocrystals (NCs) with bright, stable, and wavelength-tunable luminescence are very promising emitters for various photonic and optoelectronic applications. Recently developed strategies for inorganic surface capping of colloidal NCs using metal chalcogenide complexes have opened new perspectives for their applications. Here we report an all-inorganic surface functionalization of highly luminescent IR-emitting PbS-CdS NCs and studies of their luminescence properties. We show that inorganic capping allows simple low-temperature encapsulation of inorganic NCs into a solution-cast IR-transparent amorphous As(2)S(3) matrix. The resulting all-inorganic thin films feature stable IR luminescence in the telecommunication wavelength region. The high optical dielectric constant of As(2)S(3) also helps reduce the dielectric screening of the radiating field inside the quantum dot, enabling fast radiative recombination in PbS-CdS NCs.     

金二元纳米晶超晶格的自组装和结构表征

The assembly of two-component nanocrystals (NCs) such as metals, magnets, and semiconductors into binary nanocrystal superlattices (BNSLs) provides a fabrication route to novel classes of materials. BNSLs with certain structures can exhibit the combined and collective properties of their building blocks and are widespread in the fields of electronics and magnetic devices. As most studies have focused on combined two-component NCs of different sizes for self-assembling BNSLs, there are a few studies on single-component NCs of different sizes for the construction of BNSLs; this is especially true for Au NCs. Noble metallic Au NCs are an excellent candidate material because of their exceptional chemical stability, catalytic activity, process ability, and metallic nature; these characteristics provide them unique size-dependent optical and electronic properties as well as a wide variety of applications in sensing, imaging, electronic devices, medical diagnostics, and cancer therapeutics owing to their strong interactions with external electromagnetic fields. Therefore, it is important to develop a simple and efficient procedure to build BNSLs with different sizes of Au NCs. In our study, we synthesized monodispersed (size distribution < 10%) 6.0, 7.3, and 9.6 nm Au NCs using dodecanethiol-stabilized 3.7 nm Au NCs as seeds through a seed-growth method in oleylamine. The obtained Au NCs exhibited morphology and nanocrystallinity (single-domain and polycrystalline) similar to those of Au seeds. As the size of Au NCs increased from 3.7 to 6.0, 7.3, and 9.6 nm, the surface plasmon resonance peaks narrowed and indicated a red shift. The oleylamine-functionalized 6.0, 7.3, and 9.6 nm Au NCs were mixed with 3.7 nm Au NCs at certain concentration ratios. Au BNSLs with AB₂ (hexagonal AlB₂ structure), AB₁₃ (NaZn₁₃ structure), and AB (cubic NaCl structure) type were obtained through the solvent evaporation method. The (001) plane of the AlB₂-type structure, (001) plane of the NaZn₁₃-type structure, and (100) plane of NaCl-type structure superlattices were observed through transmission electron microscopy (TEM). The effective particle size ratios (γ= D_small/D_large) serve as the critical determining factor in the formation of the BNSLs. The effective particle size of NCs is equal to the sum of the metal core diameter and twice the thicknesses of the surface ligand. In our study, the effective particle size D_small (Au seed) is 5.7 nm; the effective particle sizes D_large (6.0, 7.3, and 9.6 nm Au NCs) are 9.0, 10.3, and 12.6 nm, respectively. The effective particle size ratios γ were therefore calculated to be 0.63, 0.55, and 0.45, respectively. The relevant space filling principle predicted the stability of the AlB₂, NaZn₁₃, and NaCl-type structures in the range of 0.482 < γ < 0.624, 0.54 < γ < 0.625, and γ < 0.458, respectively; the experimental results adequately matched the relevant space filling principle. The investigation of such a single nanocomponent as a building block is noteworthy with regard to the structures and properties of BNSLs as well as the potential development of novel meta-materials.     

Novel Strategy for Synthesis of High Quality CdTe Nanocrystals in Aqueous Solution

A novel aqueous route for the synthesis of high-quality CdTe nanocrystals（NCs） is presented in this article. With both glutathione（GSH） and cysteine[n（GSH）：n（cysteine）=1：3] as stabilizers, high-quality CdTe NCs with controllable photoluminescence（PL） wavelength from 500 to 630 nm can be prepared within 4 h. As-prepared CdTe NCs show higher photoluminescence quantum yields（PLQY） compared with CdTe NCs prepared via other aqueous methods. When the fluorescent emission peak appeared in orange-red window, the PLQY reaches 70% or above at room temperature without any post-preparative treatment.     

Synthesis of carbon dots with a tunable photoluminescence and their applications for the detection of acetone and hydrogen peroxide

Carbon dots(CDs) with multi-color emissive properties and a high photoluminescent quantum yield(PLQY) have attracted great attention recently due to their potential applications in chemical,environmental,biological and photo-electronic fields.Solvent-dependent effect in photoluminescence provides a facial and effective approach to tune the emission of CDs.In this study,green emissive nitrogen-doped carbon dots(N-CDs) are synthesized from p-hydroquinone and ethylenediamine through a simple hydrothermal method.The as-prepared N-CDs possess a robust excitation-independent green luminescence and a high PLQY of up to 15.9%.Further spectroscopic characterization indicates that the high PLQY is achieved by the balance of nitrogen doping states and the surface passivation extent in CDs.The N-CDs also exhibit solvent-dependent multi-color emissive property and distinct PLQY in different solvents(the maximum can reach up to 25.3%).Furthermore,the as-prepared N-CDs are applied as fluorescence probes to detect acetone and H2O2 in water.This method has exhibited a low detection limit of acetone(less than 0.1 %) and a quick and linear response to the H_2O_2 with the concentration from 0 to 120 μmol/L.This work broadens the knowledge of applying CDs as probes in the bio and chemical sensing fields.     

Ru修饰Pd二十四面体纳米晶的合成及其甲醇电催化氧化性能

表面结构控制和表面异种金属修饰是调控催化剂反应性的重要方法。因此,我们结合高指数晶面结构的高反应性与表面修饰异种金属,合成具有{730}高指数晶面的钯二十四面体纳米晶,并通过循环伏安扫描电沉积法得到Ru修饰的钯二十四面体纳米晶。电化学测试结果表明,低的Ru覆盖度(θ_(Ru)=0.08)可显著提高对碱性介质中甲醇电氧化的催化性能。电化学原位红外光谱结果表明,少量Ru的修饰没有减少CO的生成,而是促进了低电位下甲醇氧化成甲酸根。     

Preparation and Luminescence Properties of Color-tunable Single-phased LaPO4: Eu3+/Tb3+ Phosphors

A novel series of color-tunable single-phased phosphors La_1-x-yPO₄:xEu³⁺/yTb³⁺(x=0, 0.01, 0.02, 0.03, 0.04, 0.05; y=0, 0.05, 0.10, 0.15, 0.20) was synthesized via microwave-assisted co-precipitation method with diammonium hydrogen phosphate as precipitant. The morphology, crystal structure and photoluminescence properties of the as-prepared samples were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) and fluorescence spectrophotometer. The results reveal that the as-synthesized samples calcined at 1100℃ display spherical morphology with uniform distribution. Upon excitation with 350 nm ultraviolet radiation, the LaPO₄:Eu³⁺/Tb³⁺ phosphors showed a green light peaking at 543 nm assigned to the characteristic ⁵D₄-⁷F₅ emission of Tb³⁺ and a red light peaking at 591 nm corresponding to the characteristic ⁵D₀-⁷F₁ emission of Eu³⁺ simultaneously. For the Eu³⁺/Tb³⁺ co-activated phosphors, Tb³⁺ acts as an efficient sensitizer to enhance the emission intensity of Eu³⁺ ions. The energy transfer mechanism and the emission color tunability of LaPO₄:Eu³⁺/Tb³⁺ have been studied. The results indicate that a color-tunable luminescence(from green to white to red) can be achieved by adjusting the Eu³⁺/Tb³⁺ doping ratio in the LaPO₄ host matrix.     

非绝热分子动力学模拟A位阳离子对钙钛矿热载流子弛豫的影响

钙钛矿具有优异的光学和电学性质, 近年来成为太阳能电池领域的研究热点. 大量实验报道钙钛矿热载流子弛豫时间变化顺序为CsPbBr₃>MAPbBr₃(MA=CH₃NH₃)>FAPbBr₃[FA=HC(NH₂)₂], 但A位阳离子(Cs ⁺, MA ⁺, FA ⁺)对弛豫快慢的影响机制仍不明确. 采用基于含时密度泛函理论的非绝热动力学方法研究了上述3种钙钛矿热电子和热空穴的能量弛豫动力学, 计算得到的热载流子弛豫时间与实验结果吻合. 结果表明, A位阳离子通过静电和氢键作用影响其与无机Pb—Br骨架的电子-振动耦合, 使非绝热耦合强度遵从FAPbBr₃>MAPbBr₃>CsPbBr₃的变化趋势, 进而使热载流子弛豫时间尺度变化趋势与之相同, 表明合理选择A位阳离子可以优化钙钛矿太阳能电池的性能.     

CuInS2/CdS基掺杂纳米晶的晶体结构、光谱性质及性能调控研究

多功能纳米晶的制备、性能及其应用是材料、化学、能源、生物医学等领域十分关注的课题之一。基于掺杂调控纳米晶生长和性能的思想,发展了纳米晶修饰和复合的概念和技术,使用绿色安全的化学溶液法结合外延生长技术合成了巯基丙酸(MPA)包覆的掺杂CuInS₂/CdS基纳米晶材料。通过适当调整掺杂异价离子的种类,实现了对CuInS₂/CdS基纳米晶显微结构和性能的调控,获得了具有特定相结构、组分、尺度和光学性能(吸收性质、光学带隙、发光强度)的纳米晶。存在于基质晶体中不同金属掺杂离子,会造成半导体的禁带中间产生掺杂能级,导致二次跃迁,进而产物体现出不同的禁带宽度。掺杂Co ²⁺、Fe ²⁺、Er ³⁺离子的CuInS₂/CdS纳米晶光致发光(PL)峰强度降低明显,这是由于Co ²⁺、Fe ²⁺、Er ³⁺离子掺杂有效地抑制了空穴-电子对的复合,降低了纳米晶的光生电子-空穴复合几率,使得其光催化活性得到增强。这些半导体纳米材料在光催化、能量转换与储存方面具有良好的应用潜力。