提高钙钛矿量子点稳定性的研究进展

钙钛矿量子点具有发光谱带较窄、发光可调、量子效率高等优异的光学性能,在发光二极管、激光发射器等领域广受关注。但是钙钛矿量子点由于强离子性、高表面能及表面配体易迁移等特性而对环境高度敏感,使其在实际应用中受到限制。本文简要介绍了钙钛矿量子点结构和不稳定的原因,综述了近年来提高钙钛矿量子点稳定性的主要方法,重点从离子掺杂、表面钝化、表面包覆及多重保护4个方面展开论述。最后从绿色环保的角度出发,对高稳定生物质基钙钛矿量子点材料的制备进行了展望,提出使用具有特定结构的生物质材料及其衍生材料取代传统石油基试剂作为配体、溶剂或吸附重金属离子的外壳材料,可加速钙钛矿量子点朝着绿色低毒的方向发展。     

Single InGaAs Quantum Dot Coupling to the Plasmon Resonance of a Metal Nanocrystal

We report the observation of coupling of single InGaAs quantum dots with the surface plasmon resonance of a metal nanocrystal, which leads to clear enhancement of the photoluminescence in the spectral region of the surface plasmon resonance of the metal structures. Sharp emission lines, typical for single quantum dot emission, are observed, whereas for reference samples, only weak continuous background emission is visible. The composite metal–semiconductor structure is prepared by molecular beam epitaxy utilizing the principle of strain-driven adatom migration for the positioning of the metal nanocrystals with respect to the quantum dots without use of any additional processing steps.     

Honeycomb architecture of carbon quantum dots: a new efficient substrate to support gold for stronger SERS

The rational assembly of quantum dots (QDs) in a geometrically well-defined fashion opens up the possibility of accessing the full potential of the material and allows new functions of the assembled QDs to be achieved. In this work, well-confined two-dimensional (2D) and 3D carbon quantum dot (CQD) honeycomb structures have been assembled by electrodeposition of oxygen-rich functional CQDs within the interstitial voids of assemblies of SiO(2) nanospheres, followed by extraction of the SiO(2) cores with HF treatment. Although made from quantum sized carbon dots, the CQD assemblies present a solid porous framework, which can be further used as a sacrificial template for the fabrication of new nanostructures made from other functional materials. Based on the unique honeycomb architecture of the CQDs, which allows the more efficient adsorption of molecules, the formed Au nanoparticles on the CQD honeycomb exhibit 8-11 times stronger surface enhanced Raman scattering (SERS) effect than the widely used Au nanoparticle SERS substrate for the highly sensitive detection of target molecules. This work provides a new approach for the design and fabrication of ultrasensitive SERS platforms for various applications.     

Janus石墨烯量子点在生物膜中的输运行为：分子动力学模拟

作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。     

Janus石墨烯量子点在生物膜中的输运行为：分子动力学模拟

作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。     

铜离子掺杂CsPbCl3量子点光学性能及稳定性探究

近年来,钙钛矿因其特殊的结构受到广泛的关注。其中,全无机钙钛矿量子点作为下一代发光材料更因其优异的发光性能得到了广泛的研究和关注。但是因为其本身的铅（Pb）元素带来的毒性和较差的稳定性,钙钛矿量子点在生产和应用方面依然面临着诸多阻碍。为了解决这些难题,介绍了一种铜离子（Cu²⁺）B位掺杂CsPbCl₃钙钛矿量子点。采用了热注射的方法成功地将Cu²⁺引入CsPbCl₃钙钛矿量子点中。研究发现,Cu²⁺掺杂CsPbCl₃量子点能够保持初始四方晶体结构。由于Cu²⁺的掺杂,有效地消除了CsPbCl₃量子点的表面缺陷,从而通过辐射途径促进了激子复合,提高了CsPbCl₃量子点的发光性质。通过稳定性对比测试发现,一段时间内,Cu²⁺掺杂CsPbCl₃量子点在水中的发光强度明显高于CsPbCl₃量子点。     

Analysis of the 3D distribution of stacked self-assembled quantum dots by electron tomography

The 3D distribution of self-assembled stacked quantum dots (QDs) is a key parameter to obtain the highest performance in a variety of optoelectronic devices. In this work, we have measured this distribution in 3D using a combined procedure of needle-shaped specimen preparation and electron tomography. We show that conventional 2D measurements of the distribution of QDs are not reliable, and only 3D analysis allows an accurate correlation between the growth design and the structural characteristics.     

Hierarchical self-assembly of CdTe quantum dots into hyperbranched nanobundles: suppression of biexciton Auger recombination

In this paper, we report a novel nanobundle structure formed by the hierarchical self-assembly of TGA-capped CdTe quantum dots. HR-TEM confirms the polycrystalline phase of the bundle structure, and that pristine quantum dots are the building units. The steady state absorption and luminescence properties of the pristine quantum dots can be well inherited by the nanobundles. In transient state observation, carrier quenching induced by Auger recombination is found to be remarkably suppressed. Electron delocalizing to close building units is considered to be the reason. Suppression of Auger recombination may earn much more time for charge separation, which makes the novel nanobundle structures suitable for the excellent donor material in solar cell applications.     

铝铋离子掺杂对ZnO量子点荧光性能的影响研究

以二水合醋酸锌作为前驱体,无水乙醇作为溶剂,聚乙二醇(PEG-400)作为分散稳定剂,利用一种简单温和的方法制备Al~(3+)、Bi~(3+)掺杂氧化锌量子点,分别研究Al~(3+)、Bi~(3+)单掺,共掺对量子点荧光光谱性能的影响。结果表明:在紫外灯照射下,量子点颜色为绿色。在360 nm的激发下,ZnO量子点在524 nm附近有较的发射峰。随着掺杂离子用量的增加,ZnO量子点可见光区发射峰形状不变,单掺和共掺Al~(3+)、Bi~(3+)都使ZnO量子的荧光峰值减弱,但单掺Al~(3+)使荧光峰发生了红移。     

硅基纳米b-SiC量子点列阵的制备

报道了用两步自组装法制备硅基纳米碳化硅量子点列阵. 先将两种硅烷偶联剂均匀有序地偶联到洁净的单晶硅片上，其中一种偶联剂能打破C60上的碳碳双键而使C60通过偶联剂均匀有序地分布在硅片的表面上. 然后用夹心法或覆盖法将样品在900℃的氮气氛中退火20 min，使C60分解成活性碳，与周围的硅原子结合生成碳化硅，碳化硅分子的自组装形成了碳化硅纳米晶粒(量子点)，C60在硅表面的有序排列导致了纳米碳化硅量子点列阵形成.     

Precipitation and Optical Properties of CsPbBr3 Quantum Dots in Phosphate Glasses

CsPbBr₃ quantum dots were precipitated in phosphate glasses through heat treatment. Controlled formation of CsPbBr₃ quantum dots was realized by adjustment of heat‐treatment conditions. Absorption and photoluminescence spectra of CsPbBr₃ quantum dots were tuned from 432 to 521 nm. Upon ultraviolet or blue light excitation, efficient photoluminescence from these CsPbBr₃ quantum dots doped phosphate glasses was observed.     

Synthesis and characterization of luminescent cadmium selenide/zinc selenide/zinc sulfide cholinomimetic quantum dots

Luminescent quantum dots conjugated with highly selective molecular recognition ligands are widely used for targeting and imaging biological structures. In this paper, water soluble cholinomimetic cadmium selenide (core), zinc selenide/zinc sulfide (shell) quantum dots were synthesized for targeting cholinergic sites. Cholinomimetic specificity was incorporated by conjugation of the quantum dots to an aminated analogue of hemicholinium-15, a well known competitive inhibitor of the high affinity choline uptake transporter. Detailed evaluation of the nanocrystal synthesis and characterization of the final product was conducted by (1)H and (31)P NMR, absorption and emission spectroscopy, as well as transmission electron microscopy.     

Growth kinetics of MPS-capped CdS quantum dots in self-assembled thin films

For this study, we prepared colloidal CdS quantum dots using 3-mercaptopropyltrimethoxysilane as capping agent. Colloidal CdS quantum dots were directly deposited on glass substrates by a spin-coating process. Coated substrates were heat-treated between 225°C and 325°C for various heat treatment time intervals to investigate the growth kinetics of the quantum dots. Results showed that sizes of the CdS quantum dots grew approximately from 2.9 to 4.6 nm, and the E_1s1s energy values shifted approximately from 3.3 to 2.7 eV. Results showed that the average size of quantum dots increase by thermal treatment due to Ostwald ripening. The thermal process used to grow the size of quantum dots was examined according to the Lifshitz-Slyozov-Wagner theory. The activation energy of CdS quantum dots in thin films was calculated at approximately 44 kJ/mol.     

荧光硫量子点制备及应用研究进展

硫量子点具有发光强度高、毒性低和光化学性能稳定等优势，广泛应用于细胞成像、光电转换和化学催化等领域。鉴于此，本文系统综述了硫量子点的合成方法，光学性能和应用背景。硫量子点的合成方法可分为“自下而上法”和“自上而下法”，对比发现“自上而下法”合成的硫量子点具有更高的荧光量子产率。分析了硫量子点的光学性质，表明其具有紫外吸收特性、荧光特性、光致发光、电化学发光以及光学稳定性。最后，系统介绍了硫量子点在荧光探针、生物成像以及发光器件等领域的重要应用。基于以上分析，深刻剖析了当下硫量子点在前沿应用中亟待解决的问题，展望了未来硫量子点在生物医学、光电催化等新行业、新领域的发展方向。     

Interaction of Water-Soluble CdTe Quantum Dots with Bovine Serum Albumin

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but it is very little known about interaction of quantum dots with biological molecules. In this study, interaction of CdTe quantum dots coated with thioglycolic acid (TGA) with bovine serum albumin was investigated. Steady state spectroscopy, atomic force microscopy, electron microscopy and dynamic light scattering methods were used. It was explored how bovine serum albumin affects stability and spectral properties of quantum dots in aqueous media. CdTe–TGA quantum dots in aqueous solution appeared to be not stable and precipitated. Interaction with bovine serum albumin significantly enhanced stability and photoluminescence quantum yield of quantum dots and prevented quantum dots from aggregating.     

水性CdTe量子点在肝癌细胞标记中的应用

采用一种简单的合成方法,用空气中稳定性良好的亚碲酸钠为前体,合成了高质量的CdTe量子点,发射范围从520～620 nm可调,最佳实验条件下发光效率达40%以上。用叶酸修饰的CdTe量子点作为荧光探针,成功标记肝癌细胞,实验结果表明,通过叶酸偶联的CdTe量子点,能有效进入肿瘤细胞内部。     

Plasmonics with Doped Quantum Dots

We review the discovery of localized surface plasmon resonances (LSPRs) in doped semiconductor quantum dots (QDs), an advance that has extended nanoplasmonics to materials beyond the classic gamut of noble metals. The initial demonstrations of near-infrared LSPRs in QDs of heavily self-doped copper chalcogenides and conducting metal oxides are setting the broad stage for this new field. We describe the key properties of QD LSPRs. Although the essential physics of plasmon resonances are similar to that in metal nanoparticles, the attributes of QD LSPRs represent a paradigm shift from metal nanoplasmonics. Carrier doping of quantum dots allows access to tunable LSPRs in the wide frequency range from the THz to the near-infrared. Such composition or carrier density tunability is unique to semiconductor quantum dots and not achievable in metal nanoparticles. Most strikingly, semiconductor quantum dots allow plasmon resonances to be dynamically tuned or switched by active control of carriers. Semiconducting quantum dots thus represent the ideal building blocks for active plasmonics. A number of potential applications are discussed, including the use of plasmonic quantum dots as ultrasmall labels for biomedicine and electrochromic materials, the utility of LSPRs for probing nanoscale charge dynamics in semiconductors, and the exploitation of strong coupling between photons and excitons. Further advances in this field necessitate efforts toward generalizing plasmonic phenomena to a wider range of semiconductors, developing strategies for achieving controlled levels of doping and stabilizing them, investigating the spectroscopy of these systems on a fundamental level, and exploring their integration into optoelectronic devices.     

Synthesis of MDMO-PPV capped PbS quantum dots and their application to solar cells

Poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) capped PbS quantum dots about 3-6 nm in diameter were synthesized with a novel method. Unlike the synthesis of oleic acid capped PbS quantum dots, the reactions were carried out in solution at room temperature, with the presence of a capping ligand species, MDMO-PPV. The quantum dots were used to fabricate bulk heterojunction solar cells with an indium tin oxide (ITO)/polyethylenedioxythiophene/polystyrenesulphonate (PEDOT: PSS)/MDMO-PPV: PbS/Al structure. Current density-voltage characterization of the devices showed that after the addition of the MDMO-PPV capped PbS quantum dots to MDMO-PPV film, the performance was dramatically improved compared with pristine MDMO-PPV solar cells.     

The surface termination effect on the quantum confinement and electron affinities of 3C-SiC quantum dots: a first-principles study

In light of the established differences between the quantum confinement effect and the electron affinities between hydrogen-passivated C and Si quantum dots, we carried out theoretical investigations on SiC quantum dots, with surfaces uniformly terminated by C-H or Si-H bonds, to explore the role of surface terminations on these two aspects. Surprisingly, it was found that the quantum confinement effect is present (or absent) in the highest occupied (or lowest unoccupied) molecular orbital of the SiC quantum dots regardless of their surface terminations. Thus, the quantum confinement effect related to the energy gap observed experimentally (Phys. Rev. Lett., 2005, 94, 026102) is contributed to by the size-dependence of the highest occupied states; the absence of quantum confinement in the lowest unoccupied states is in contrary to the usual belief based on hydrogen-passivated C quantum dots. However, the cause of the absence of the quantum confinement in C nanodots is not transferable to SiC. We propose a model that provides a clear explanation for all findings on the basis of the nearest-neighbor and next-nearest-neighbor interactions between the valence atomic p-orbital in the frontier occupied/unoccupied states. We also found that the electron affinities of the SiC quantum dots, which closely depend on the surface environments, are negative for the C-H termination and positive for the Si-H termination. The prediction of negative electron affinities in SiC quantum dots by simple C-H termination indicates a promising application for these materials in electron-emitter devices. Our model predicts that GeC quantum dots with hydrogen passivation exhibit similar features to SiC quantum dots and our study confirms the crucial role that the surface environment plays in these nanoscale systems.     

Facile solution growth of vertically aligned ZnO nanorods sensitized with aqueous CdS and CdSe quantum dots for photovoltaic applications

Vertically aligned single crystalline ZnO nanorod arrays, approximately 3 μm in length and 50-450 nm in diameter are grown by a simple solution approach on a Zn foil substrate. CdS and CdSe colloidal quantum dots are assembled onto ZnO nanorods array using water-soluble nanocrystals capped as-synthesized with a short-chain bifuncional linker thioglycolic acid. The solar cells co-sensitized with both CdS and CdSe quantum dots demonstrate superior efficiency compared with the cells using only one type of quantum dots. A thin Al2O3 layer deposited prior to quantum dot anchoring successfully acts as a barrier inhibiting electron recombination at the Zn/ZnO/electrolyte interface, resulting in power conversion efficiency of approximately 1% with an improved fill factor of 0.55. The in situ growth of ZnO nanorod arrays in a solution containing CdSe quantum dots provides better contact between two materials resulting in enhanced open circuit voltage.