基于量子点荧光探针的高灵敏蛋白质检测方法

通过制备量子点荧光检测探针,构建了一种基于量子点探针和免疫磁珠的蛋白质检测方法,实现了对蛋白肿瘤标志物癌胚抗原(carcinoembryonic antigen,CEA)的高灵敏定量检测.在该检测体系中,若存在有靶标蛋白,其与量子点检测探针以及捕获探针之间会发生免疫反应形成三明治结构,利用磁力分离器对免疫复合物进行富集后,通过检测富集在磁珠表面的量子点荧光信号,可实现对靶标蛋白的定量.该方法的检测灵敏度为38 pg/mL,线性范围为0.39~50ng/mL,临床质控样本检验结果表明,该方法准确度高,可重复性好,可应用于临床样本检测.该量子点探针检测体系具有灵敏度高、特异性好、样品消耗量低等优点,在疾病早期诊断方面具有广阔的应用前景.     

高响应率石墨烯-CsPbBr3量子点光电探测器

全无机金属卤化物钙钛矿材料CsPbX_3(X=Cl,Br,I)不仅有优异光电特性,还有比有机-无机杂化钙钛矿更好的热稳定性,在光电探测器领域有很大应用前景.但由于全无机钙钛矿材料自身迁移率较低,直接用于光电探测器其光响应率也很低,难以满足实际应用.以热注入法合成高质量的CsPbBr_3钙钛矿量子点材料,再将其与高迁移率的单层石墨烯薄膜相结合,构建出石墨烯-CsPbBr_3量子点复合光电探测器,光响应率高达3.5×10~4 A·W~(-1).研究表明引入石墨烯材料作为传输层后,CsPbBr_3量子点的光生电子空穴对得到有效分离并快速传输.两种材料界面处存在陷阱态,产生了光栅压效应,延长了载流子寿命.两种机制结合使复合光电探测器的光响应率大大提升.     

量子点层厚度对量子点发光二极管发光特性的影响简

采用湿法旋涂技术制备量子点发光二极管器件（QD-LEDs）。PEDOT作为空穴注入层,TFB作为空穴传输层,量子点作为发光层,采用无机二氧化钛（TiO2）作为电子传输层,在相同的工艺条件下调节量子点层旋涂转速（800～1100 r/min）,制备不同厚度的量子点发光二极管发光器件（QD-LEDs）。实验结果表明,当量子点层的旋涂转速为900 r/min时,此时的量子点层厚度为30 nm,所制备的量子点发光二极管器件（QD-LEDs）的发光性能最好,开启电压最低,只有5．5 V。     

Kondo effect in an integer-spin quantum dot

The Kondo effect--a many-body phenomenon in condensed-matter physics involving the interaction between a localized spin and free electrons--was discovered in metals containing small amounts of magnetic impurities, although it is now recognized to be of fundamental importance in a wide class of correlated electron systems. In fabricated structures, the control of single, localized spins is of technological relevance for nanoscale electronics. Experiments have already demonstrated artificial realizations of isolated magnetic impurities at metallic surfaces, nanoscale magnets, controlled transitions between two-electron singlet and triplet states, and a tunable Kondo effect in semiconductor quantum dots. Here we report an unexpected Kondo effect in a few-electron quantum dot containing singlet and triplet spin states, whose energy difference can be tuned with a magnetic field. We observe the effect for an even number of electrons, when the singlet and triplet states are degenerate. The characteristic energy scale is much larger than in the ordinary spin-1/2 case.     

Ultrasensitive polarized-light photodetectors based on 2D hybrid perovskite ferroelectric crystals with a low detection limit

Polarized-light photodetectors are the indispensable elements for practical optical and optoelectronic device applications.Two-dimensional(2D)hybrid perovskite ...     

Controlling cavity reflectivity with a single quantum dot

Solid-state cavity quantum electrodynamics (QED) systems offer a robust and scalable platform for quantum optics experiments and the development of quantum information processing devices. In particular, systems based on photonic crystal nanocavities and semiconductor quantum dots have seen rapid progress. Recent experiments have allowed the observation of weak and strong coupling regimes of interaction between the photonic crystal cavity and a single quantum dot in photoluminescence. In the weak coupling regime, the quantum dot radiative lifetime is modified; in the strong coupling regime, the coupled quantum dot also modifies the cavity spectrum. Several proposals for scalable quantum information networks and quantum computation rely on direct probing of the cavity-quantum dot coupling, by means of resonant light scattering from strongly or weakly coupled quantum dots. Such experiments have recently been performed in atomic systems and superconducting circuit QED systems, but not in solid-state quantum dot-cavity QED systems. Here we present experimental evidence that this interaction can be probed in solid-state systems, and show that, as expected from theory, the quantum dot strongly modifies the cavity transmission and reflection spectra. We show that when the quantum dot is coupled to the cavity, photons that are resonant with its transition are prohibited from entering the cavity. We observe this effect as the quantum dot is tuned through the cavity and the coupling strength between them changes. At high intensity of the probe beam, we observe rapid saturation of the transmission dip. These measurements provide both a method for probing the cavity-quantum dot system and a step towards the realization of quantum devices based on coherent light scattering and large optical nonlinearities from quantum dots in photonic crystal cavities.     

Quantum phase transition in a single-molecule quantum dot

Quantum criticality is the intriguing possibility offered by the laws of quantum mechanics when the wave function of a many-particle physical system is forced to evolve continuously between two distinct, competing ground states. This phenomenon, often related to a zero-temperature magnetic phase transition, is believed to govern many of the fascinating properties of strongly correlated systems such as heavy-fermion compounds or high-temperature superconductors. In contrast to bulk materials with very complex electronic structures, artificial nanoscale devices could offer a new and simpler means of understanding quantum phase transitions. Here we demonstrate this possibility in a single-molecule quantum dot, where a gate voltage induces a crossing of two different types of electron spin state (singlet and triplet) at zero magnetic field. The quantum dot is operated in the Kondo regime, where the electron spin on the quantum dot is partially screened by metallic electrodes. This strong electronic coupling between the quantum dot and the metallic contacts provides the strong electron correlations necessary to observe quantum critical behaviour. The quantum magnetic phase transition between two different Kondo regimes is achieved by tuning gate voltages and is fundamentally different from previously observed Kondo transitions in semiconductor and nanotube quantum dots. Our work may offer new directions in terms of control and tunability for molecular spintronics.     

Real-time detection of electron tunnelling in a quantum dot

Nanostructures in which strong (Coulomb) interactions exist between electrons are predicted to exhibit temporal electronic correlations. Although there is ample experimental evidence that such correlations exist, electron dynamics in engineered nanostructures have been observed directly only on long timescales. The faster dynamics associated with electrical currents or charge fluctuations are usually inferred from direct (or quasi-direct) current measurements. Recently, interest in electron dynamics has risen, in part owing to the realization that additional information about electronic interactions can be found in the shot noise or higher statistical moments of a direct current. Furthermore, interest in quantum computation has stimulated investigation of quantum bit (qubit) readout techniques, which for many condensed-matter systems ultimately reduces to single-shot measurements of individual electronic charges. Here we report real-time observation of individual electron tunnelling events in a quantum dot using an integrated radio-frequency single-electron transistor. We use electron counting to measure directly the quantum dot's tunnelling rate and the occupational probabilities of its charge state. Our results provide evidence in favour of long (10 micros or more) inelastic scattering times in nearly isolated dots.     

量子点作为生物荧光探针的应用研究

量子点作为一种能发射荧光的半导体纳米微晶体,具有独特的光学性质。这决定了它在生物研究中有广阔的诱人的前景:如替代传统的生物荧光探针,具有荧光光谱较窄、量子产率高、不易漂白等优点;进一步讨论了量子点的电泳和微流控芯片的生物应用及其前景。     

量子点人工光合成制氢研究进展

综述了本研究组近年来量子点人工光合成制氢体系的研究进展,重点从量子点与氢化酶模拟化合物、量子点与过渡金属离子、量子点敏化光阴极3个方面分析了影响制氢效率的主要因素,指出对光生电荷(电子和空穴)的有效捕获是提高人工光合成分解水制氢效率的关键,并展望了未来人工光合成发展方向。     

量子点中双激子的关联能

采用精确对角化方法,研究了限制在半导体量子点中双激子的量子尺寸效应.计算了双激子量子点的基态和低激发态的关联能随限制强度大小变化的关系,揭示了双激子量子点的基态和低激发态能谱的重要性质.我们发现随着限制强度的增加,双激子量子点的基态和低激发态的关联能变化是不同的;我们还发现限制可以引起不同低激发态能级的偶然简并和能级的反转.这些性质都与系统的交换和旋转对称性有关.     

量子点人工光合成制氢研究进展

 综述了本研究组近年来量子点人工光合成制氢体系的研究进展，重点从量子点与氢化酶模拟化合物、量子点与过渡金属离子、量子点敏化光阴极3个方面分析了影响制氢效率的主要因素，指出对光生电荷（电子和空穴）的有效捕获是提高人工光合成分解水制氢效率的关键，并展望了未来人工光合成发展方向。     

Coherent singlet-triplet oscillations in a silicon-based double quantum dot

Silicon is more than the dominant material in the conventional microelectronics industry: it also has potential as a host material for emerging quantum information technologies. Standard fabrication techniques already allow the isolation of single electron spins in silicon transistor-like devices. Although this is also possible in other materials, silicon-based systems have the advantage of interacting more weakly with nuclear spins. Reducing such interactions is important for the control of spin quantum bits because nuclear fluctuations limit quantum phase coherence, as seen in recent experiments in GaAs-based quantum dots. Advances in reducing nuclear decoherence effects by means of complex control still result in coherence times much shorter than those seen in experiments on large ensembles of impurity-bound electrons in bulk silicon crystals. Here we report coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure and show that this system has a nuclei-induced dephasing time of 360 nanoseconds, which is an increase by nearly two orders of magnitude over similar measurements in GaAs-based quantum dots. The degree of phase coherence observed, combined with fast, gated electrical initialization, read-out and control, should motivate future development of silicon-based quantum information processors.     

Protease-activated quantum dot probes based on fluorescence resonance energy transfer

A novel sensing system based on fluorescence resonance energy transfer (FRET) between CdTe quantum dots (QDs) and Rhoda-mine B (RB) was established for the detection of matrix metalloproteinases (MMOL/LPs). In this system, 535-nm-emitting quantum dots (QDs) were bound to Rhodamine B (RB) via a MMOL/LP-specific peptide. A 76% reduction in luminescence was achieved because of FRET. Release of RBs by peptide cleavage restores radiative QD photoluminescence. Initial studies observed a 73% rise in luminescence over 60 min. The design platform of the nanosensor is flexible and can be fine-tuned for a wide array of applications such as the detection of biomarkers, early diagnosis of disease, and monitoring therapeutic efficacy simply by changing the sequence of the peptide linker.     

微波场作用下Fano效应对量子点电子态密度近藤峰的影响

讨论了一个微波场辐照下量子点电极耦合体系,当两边电极间存在非共振直接隧穿时量子．占、上电子态密度的变化情况。用非平衡格林函数方法及吴大琪假设得到了此体系能态密度在相互作用强度U有限情况下的解析表达式。数值计算的结果表明随着背景透射率及库仑相互作用能大小的变化,量子点上电子能态密度共振峰可被增强或减弱,并可能出现新的共振峰结构。     

利用回音壁微腔系统克服量子点能级自然分裂

用一种全量子理论方法研究了一回音壁微腔-V型三能级量子点系统之间的耦合.量子点分别由基态、左圆极化激子态和右圆极化激子态构成,两简并回音壁腔模分别与左激子跃迁模和右激子跃迁模相耦合,其耦合率分别为gL和gR.在实空间里,我们推导了透射模与反射模的精确解,并得出其数值结果.结果显示了复合系统的耦合动力学特性;更重要的是,我们可以通过设计微腔得到合适的微腔反向散射率?,利用双模与量子点强耦合,就可以克服双激子能级精细结构的分裂(FSS).     

Triplet-singlet spin relaxation via nuclei in a double quantum dot

The spin of a confined electron, when oriented originally in some direction, will lose memory of that orientation after some time. Physical mechanisms leading to this relaxation of spin memory typically involve either coupling of the electron spin to its orbital motion or to nuclear spins. Relaxation of confined electron spin has been previously measured only for Zeeman or exchange split spin states, where spin-orbit effects dominate relaxation; spin flips due to nuclei have been observed in optical spectroscopy studies. Using an isolated GaAs double quantum dot defined by electrostatic gates and direct time domain measurements, we investigate in detail spin relaxation for arbitrary splitting of spin states. Here we show that electron spin flips are dominated by nuclear interactions and are slowed by several orders of magnitude when a magnetic field of a few millitesla is applied. These results have significant implications for spin-based information processing.     

基于动态光散射法测量量子点粒径的实验方法

动态光散射技术是进行纳米及亚微米颗粒粒径测量的一种有效方法.通过对量子点特性和动态光散射系统的分析,提出了一种基于动态光散射测量量子点粒径的实验方法,构建实验装置并进行测量与分析.通过CONTIN算法反演量子点粒径,并与电子显微镜和粒径公式得到的粒径数据进行比较,证明动态光散射法是测量量子点粒径的一种有效的方法,为量子点光学特性的快速分析提供了一种新的途径.     

与铁磁导体耦合的量子点中非线性热自旋效应

研究与两个铁磁导体耦合的单个量子点中热梯度产生的纯自旋流。发现热梯度和电子库的铁磁性会在量子点能级离开电子-空穴对称点时产生较强的自旋压。自旋压的大小和方向可以通过改变热梯度的方向来调整。当两个铁磁引线的磁化方向为相互平行时,自旋压的绝对值最小,而当两个引线中的磁矩为反平行时,自旋压的强度会显著增大。