圆偏振光诱导CdTe量子点再生长及其对光致发光的影响

实验研究了以3-巯基丙酸为配体合成的水溶性CdTe量子点经过非偏振光与圆偏振光照射处理后, 量子点的再生长变化规律。采用光致发光谱、紫外-可见吸收光谱、透射电子显微镜与X射线衍射等表征手段分析表明: 非偏振光会促进CdTe量子点的光氧化, 导致量子点尺寸缩小, 荧光发光峰位蓝移, 且发光效率降低; 而圆偏振光增强了配体的光氧化, 在量子点表面形成CdS层, 导致量子点尺寸进一步增大, 荧光发光峰红移, 且发光效率提升。进一步讨论了CdTe量子点与配体之间的键合作用, 相关光化学反应机制及其对量子点光致发光性质的影响。     

N-B-Al共掺荧光4H-SiC施主受主对发光性能研究

施主受主共掺杂的荧光4H-SiC可以通过复合发出可见光, 影响其发光性能的一个重要因素是施主-受主掺杂的浓度。本研究通过PVT生长方法制备了3英寸N-B-Al共掺的4H-SiC晶体, 采用Raman光谱、SIMS对晶体的结晶类型和掺杂浓度进行了表征; 采用PL发射谱和激发谱、荧光衰减曲线表征和内量子效率对晶体的发光波长、强度、施主-受主对复合发光性能进行了研究。结果发现, 低浓度Al掺杂样品在室温下发出黄绿色荧光。低浓度Al掺杂在晶体中提供较少的受主; 高浓度B、N掺杂形成施主, 从而贡献充足的电子-空穴对。这些电子-空穴的复合提高了施主-受主对复合的内量子效率, 进而增强光致发光强度, 增加平均发光寿命。     

Photoluminenscence Blinking Dynamics of Colloidal Quantum Dots in the Presence of Controlled External Electron Traps

The effect of the external charge trap on the photoluminescence blinking dynamics of individual colloidal quantum dots is investigated with a series of colloidal quantum dot–bridge–fullerene dimers with varying bridge lengths, where the fullerene moiety acts as a well‐defined, well‐positioned external charge trap. It is found that charge transfer followed by charge recombination is an important mechanism in determining the blinking behavior of quantum dots when the external trap is properly coupled with the excited state of the quantum dot, leading to a quasi‐continuous distribution of ‘on' states and an early fall‐off from a power‐law distribution for both ‘on' and ‘off' times associated with quantum dot photoluminescence blinking.     

Temperature‐Dependent Exciton and Trap‐Related Photoluminescence of CdTe Quantum Dots Embedded in a NaCl Matrix: Implication in Thermometry

Temperature‐dependent optical studies of semiconductor quantum dots (QDs) are fundamentally important for a variety of sensing and imaging applications. The steady‐state and time‐resolved photoluminescence properties of CdTe QDs in the size range from 2.3 to 3.1 nm embedded into a protective matrix of NaCl are studied as a function of temperature from 80 to 360 K. The temperature coefficient is found to be strongly dependent on QD size, with the highest sensitivity obtained for the smallest size of QDs. The emission from solid‐state CdTe QD‐based powders is maintained with high color purity over a wide range of temperatures. Photoluminescence lifetime data suggest that temperature dependence of the intrinsic radiative lifetime in CdTe QDs is rather weak, and it is mostly the temperature‐dependent nonradiative decay of CdTe QDs which is responsible for the thermal quenching of photoluminescence intensity. By virtue of the temperature‐dependent photoluminescence behavior, high color purity, photostability, and high photoluminescence quantum yield (26%–37% in the solid state), CdTe QDs embedded in NaCl matrices are useful solid‐state probes for thermal imaging and sensing over a wide range of temperatures within a number of detection schemes and outstanding sensitivity, such as luminescence thermochromic imaging, ratiometric luminescence, and luminescence lifetime thermal sensing.     

Magnetic-field tuning of the alloy-induced disorder in quaternary semimagnetic (Zn, Cd, Mn)Se quantum well structures

The influence of magnetic-field-induced tuning of the disorder on the line width of the lowest excitonic transition in diluted magnetic semiconductor (Zn, Cd, Mn)Se/ZnSe quantum well samples is studied by photoluminescence at 2 K and in magnetic fields up to 7.5 T. It is shown that the dependence of the photoluminescence line width on quantum well thickness can be explained as a sum of contributions of ZnSe barrier, (Zn, Cd, Mn)Se well and the interfaces.     

镶嵌在SiO2薄膜中的锗纳米晶粒的光致发光

采用６３０ｎｍ波长的激发光在室温下对镶嵌有锗纳米晶的ＳｉＯ２薄膜进行了光致姚研究。在室温下观察到了由于双光子吸收而导致的蓝色荧光峰。按照量子限域理论对所观察到的峰的特征进行了讨论。     

CdS／PAMAM纳米复合材料的制备及光学性能

以聚酰胺－胺（PAMAM）树形分子为模板，原位合成CdS，AMAM树形分子纳米复合材料，探索不同负载比对其性能的影响及量子点表面的功能性。通过荧光光谱技术，分析Cu^2＋和Mn^2＋重金属离子对其光致发光性能的影响，利用光学性质变化、材料分析稳定度考察其反应机制。     

Anomalous Magneto-Optical Properties of EuTe Induced by Magnetic Polarons

We report the magneto-optical studies on the EuTe epilayer grown by molecular beam epitaxy. Huge Zeeman shift of the excitonic photoluminescence is observed. The circular polarization property of the photoluminescence is investigated. An evident hysteresis behavior of the circular polarization for the excitonic photoluminescence is resolved, indicating the existence of the initial magnetization due to the formation of dense bound magnetic polaron.     

水溶性ZnSe纳米晶的微波制备与表征(英文)

本文利用微波辐射方法,在水相中直接快速制备,得到了谷胱甘肽修饰的水溶性ZnSe纳米晶,并详细讨论了制备条件(溶液中离子配比、PH值、反应温度和时间等)对结果的影响.在最佳条件下制备所得的ZnSe纳米晶,发射波长在360nm～410nm之间可调,荧光光谱半峰宽最小值可达到21nm.另外,进一步利用光辐射方法,对ZnSe纳米晶进行表面修饰,将其荧光量子效率提高到了55%.本文制备方法具有过程简单、经济的优点,此外,这种水溶性ZnSe纳米晶具有优良的光谱性能和良好的生物相溶性,可使其作为荧光探针进一步应用在生物领域.     

Photoluminescence of CdSe nanowires grown with and without metal catalyst

We present temperature and power dependent photoluminescence measurements on CdSe nanowires synthesized via vapor-phase with and without the use of a metal catalyst. Nanowires produced without a catalyst can be optimized to yield higher quantum efficiency, and narrower and spatially uniform emission, when compared to the catalyst-assisted ones. Emission at energies lower than the band-edge is also found in both cases. By combining spatially-resolved photoluminescence and electron microscopy on the same nanowires, we show that catalyst-free nanowires exhibit a low-energy peak with sharp phonon replica, whereas for catalyst-assisted nanowires low-energy emission is linked to the presence of nanostructures with extended morphological defects.      

Alloyed Mn-Cu-In-S nanocrystals: a new type of diluted magnetic semiconductor quantum dots

A new type of Mn-Cu-In-S diluted magnetic semiconductor quantum dots was synthesized and reported for the first time. The quantum dots, with no highly toxic elements, not only show the same classic diluted magnetic behavior as Mn-doped CdSe, but also exhibit tunable luminescent properties in a relatively large window from 542 to 648?nm. An absolute photoluminescence quantum yield up to 20% was obtained after the shell growth of ZnS. This kind of magnetic/luminescent bi-functional Mn-Cu-In-S/ZnS core/shell quantum dot might serve as promising nanoprobes for use in dual-mode optical and magnetic resonance imaging techniques.     

Growth and Spectroscopy of CdSe: Mn Quantum Dots

In this paper we report the growth and optical properties of ZnSe/CdSe:Mn magnetic quantum dots by Atomic Layer Epitaxy. For the uncapped samples, dot densities of the order of 10⁹ cm^–2 were measured by Atomic Force Microscopy. The ensemble dot photoluminescence (PL) was observed over a range of energies between 2.1 and 2.5 eV, and a spectrally broad emission at 2.15 eV from the internal Mn²⁺ transition was observed at high Mn concentrations. Single dot spectroscopy was carried out by confocal microscopy and the PL line width was measured as a function of Mn concentration. For large Mn contents the temporal change in magnetization causes a broadening of the single dot PL line of up to 4 meV FWHM. However, for low concentrations the single dot PL line widths were resolution limited at <0.2 meV.     

Two-fold emission from the S-shell of PbSe/CdSe core/shell quantum dots

The optical properties of PbSe/CdSe core/shell quantum dots with core sizes smaller than 4 nm in the 5-300 K range are reported. The photoluminescence spectra show two peaks, which become increasingly separated in energy as the core diameter is reduced below 4 nm. It is shown that these peaks are due to intrinsic exciton transitions in each quantum dot, rather than emission from different quantum dot sub-ensembles. Most likely, the energy separation between the peaks is due to inter-valley coupling between the L-points of PbSe. The temperature dependence of the relative intensities of the peaks implies that the two emitting states are not in thermal equilibrium and that dark exciton states must play an important role.     

Size Controlled Synthesis of Silicon Nanocrystals Using Cationic Surfactant Templates

Alkyl‐terminated silicon nanocrystals (Si NCs) are synthesized at room temperature by hydride reduction of silicon tetrachloride (SiCl₄) within inverse micelles. Highly monodisperse Si nanocrystals with average diameters ranging from 2 to 6 nm are produced by variation of the cationic quaternary ammonium salts used to form the inverse micelles. Transmission electron microscopy imaging shows that the NCs are highly crystalline, while FTIR spectra confirm that the NCs are passivated by covalent attachment of alkanes, with minimal surface oxidation. UV‐vis absorbance and photoluminescence spectroscopy show significant quantum confinement effects, with moderate absorption in the UV spectral range, and a strong blue emission with a marked dependency on excitation wavelength. The photoluminescence quantum yield (Φ) of the Si NCs exhibits an inverse relationship with the mean NC diameter, with a maximum of 12% recorded for 2 nm NCs.     

Thermally Activated Photoluminescence in Lead Selenide Colloidal Quantum Dots

The thermal activation processes in PbSe colloidal quantum dots and their influence on the ground‐state exciton emission are discussed. Activation of a dark exciton occurs at 1.4–7 K, assisted by an acoustic phonon coupling. Activation of a bright exciton occurs at 100–200 K, which appears as a sudden change in the photoluminescence band intensity, energy, and full width at half maximum. This activation overcomes the dark–bright‐state splitting, when the activation temperature increases with the decrease of the dots' size. The dark exciton lifetime is found to be ≈6–12 µs at 1.4 K, while the bright exciton lifetime at 300 K evaluated as 450 ns varies slightly with the change in the size of the dots. In addition, the emission quantum yield of these dots, measured at a variety of temperatures when dissolved in various solvents, reveals information about the influence of the environment on the recombination processes.     

离子注入对纳米Si_3N_4结构的影响

通过ＦＴ－ＩＲ、ＸＰＳ和荧光光谱研究了离子注入对纳米Ｓｉ３Ｎ４结构的影响．发现离子注入改变了材料中游离硅（ａ－Ｓｉ）的结构,使其变成了ＳｉＮｎ（ｎ＝１,２）．荧光谱研究表明纳米Ｓｉ３Ｎ４具有明显的量子限制效应,并且荧光峰的位置和强度存在不稳定性．根据实验结果给出了纳米Ｓｉ３Ｎ４的能级结构图.     

Origin of visible photoluminescence from porous silicon as studied by Raman spectroscopy

In this paper we discuss the different models proposed to explain the visible luminescence in porous silicon (PS). We review our recent photoluminescence and Raman studies on PS as a function of different preparation conditions and isochronal thermal annealing. Our results can be explained by a hybrid model which incorporates both nanostructures for quantum confinement and silicon complexes (such as SiH _x and siloxene) and defects at Si/SiO₂ interfaces as luminescent centres.     

Photolithographic Patterning of Organic Color-Centers

Organic color-centers (OCCs) have emerged as promising single-photon emitters for solid-state quantum technologies, chemically specific sensing, and near-infrared bioimaging. However, these quantum light sources are currently synthesized in bulk solution, lacking the spatial control required for on-chip integration. The ability to pattern OCCs on solid substrates with high spatial precision and molecularly defined structure is essential to interface electronics and advance their quantum applications. Herein, a lithographic generation of OCCs on solid-state semiconducting single-walled carbon nanotube films at spatially defined locations is presented. By using light-driven diazoether chemistry, it is possible to directly pattern p-nitroaryl OCCs, which demonstrate chemically specific spectral signatures at programmed positions as confirmed by Raman mapping and hyperspectral photoluminescence imaging. This light-driven technique enables the fabrication of OCC arrays on solid films that fluoresce in the shortwave infrared and presents an important step toward the direct writing of quantum emitters and other functionalities at the molecular level.     

Lead‐Free Halide Rb2CuBr3 as Sensitive X‐Ray Scintillator

Scintillators are widely utilized for radiation detections in many fields, such as nondestructive inspection, medical imaging, and space exploration. Lead halide perovskite scintillators have recently received extensive research attention owing to their tunable emission wavelength, low detection limit, and ease of fabrication. However, the low light yields toward X‐ray irradiation and the lead toxicity of these perovskites severely restricts their practical application. A novel lead‐free halide is presented, namely Rb₂CuBr₃, as a scintillator with exceptionally high light yield. Rb₂CuBr₃ exhibits a 1D crystal structure and enjoys strong carrier confinement and near‐unity photoluminescence quantum yield (98.6%) in violet emission. The high photoluminescence quantum yield combined with negligible self‐absorption from self‐trapped exciton emission and strong X‐ray absorption capability enables a record high light yield of ≈91056 photons per MeV among perovskite and relative scintillators. Overall, Rb₂CuBr₃ provides nontoxicity, high radioluminescence intensity, and good stability, thus laying good foundations for potential application in low‐dose radiography.     

掺Mn硅酸锌薄膜中微量氧化锌对发光强度的影响

利用溶胶-凝胶法结合高温热处理在硅衬底上制备了掺Mn硅酸锌薄膜，用XRD、SEM、UV-Vis吸收谱和PL谱测试了样品的结晶性能与光学性能，并分析了热处理温度对掺Mn硅酸锌薄膜的结晶性能和光学性能的影响．实验结果发现，ZnO的适量存在对掺Mn薄膜的发光有增强作用．进一步的分析认为，这一现象的机理可由G．G．Qin提出的量子约束-发光中心（QCLC）模型进行解释，ZnO中受激发的电子和空穴通过隧穿效应到达硅酸锌基体中复合发光，从而增强发光强度．