Long-lasting photoluminescence quantum yield of cesium lead halide perovskite-type quantum dots

Cesium lead halide perovskite(CsPbX₃,X=Cl,Br,I)quantum dots(QDs)and their partly Mn²⁺-substituted QDs(CsPb1–xMnxX3)attract considerable attention owing to their unique photoluminescence(PL)efficiencies.The two types of QDs,having different PL decay dynamics,needed to be further investigated in a form of aggregates to understand their solid-state-induced exciton dynamics in conjunction with their behaviors upon degradation to achieve practical applications of those promising QDs.However,thus far,these QDs have not been sufficiently investigated to obtain deep insights related to the long-term stability of their PL properties as aggregated solid-states.Therefore,in this study,we comparatively examined CsPbX₃-and CsPb1–xMnxX₃-type QDs stocked for>50 d under dark ambient conditions by using excitation wavelength-dependent PL quantum yield and time-resolved PL spectroscopy.These investigations were performed with powder samples in addition to solutions to determine the influence of the inter-QD interaction of the aged QD aggregates on their radiative decays.It turns out that the Mn²⁺-substituted QDs exhibited long-lasting PL quantum efficiencies,while the unsubstituted CsPbX₃-type QDs exhibited a drastic reduction of their PL efficiencies.And the obtained PL traces were clearly sensitive to the sample status.This is discussed with the possible interaction depending on the size and distance of the QD aggregates.     

Are quantum dots ready for in vivo imaging in human subjects?

Nanotechnology has the potential to profoundly transform the nature of cancer diagnosis and cancer patient management in the future. Over the past decade, quantum dots (QDs) have become one of the fastest growing areas of research in nanotechnology. QDs are fluorescent semiconductor nanoparticles suitable for multiplexed in vitro and in vivo imaging. Numerous studies on QDs have resulted in major advancements in QD surface modification, coating, biocompatibility, sensitivity, multiplexing, targeting specificity, as well as important findings regarding toxicity and applicability. For in vitro applications, QDs can be used in place of traditional organic fluorescent dyes in virtually any system, outperforming organic dyes in the majority of cases. In vivo targeted tumor imaging with biocompatible QDs has recently become possible in mouse models. With new advances in QD technology such as bioluminescence resonance energy transfer, synthesis of smaller size non-Cd based QDs, improved surface coating and conjugation, and multifunctional probes for multimodality imaging, it is likely that human applications of QDs will soon be possible in a clinical setting.     

Design considerations for highly efficient edge‐lit quantum dot displays

Quantum dots (QDs) are increasingly the technology of choice for wide color gamut displays. Two popular options to incorporate QDs into displays include on‐edge and on‐surface solutions. The opto‐mechanical design for an on‐edge QD solution including a LED light bar (“on‐edge QD light bar”) is more complex than the design for a standard white phosphor LED light bar. In this paper, we identify and investigate a range of design parameters for an on‐edge QD light bar, and we show that these parameters have significant influence on system efficiency and color uniformity. The effects of varying these parameters are explored through the use of a custom adjustable testbed and optical raytracing methods. Our testbed data demonstrate the inherent trade‐offs between efficiency and color uniformity and provide guidance for the design of high‐performing displays. The optical raytracing data demonstrate a good predictive capability and support the use of optical modeling methods for a detailed exploration of a wider range of design parameters.     

三元离子交换平衡的表达与计算

利用Ｐｉｔｚｅｒ电解质溶液模型和Ｆｒａｎｋｉｌｎ三元交换体系的表达方法,对ＷＱＤ １沸石的Ｋ＋ Ｎａ＋ ＮＨ４＋交换平衡进行了定量描述。计算结果表明：在海水提钾等交换前后离子浓度变化不大的情况下,液相活度校正项可近似为１。经过简化后的离子交换平衡商可代替交换选择商Ｋｋ＋／Ｎａ＋。     

1.3 μm InAs quantum dot resonant cavity light emitting diodes

Resonant cavity light emitting diodes (RCLEDs) containing nine sheets of self-organized InAs quantum dot (QD) active layers and operating at around 1.3 μm are demonstrated. The structure was grown directly on GaAs substrates, which includes selectively oxidized AlO_x current apertures and intracavity metal contacts. It was found that the average operating resistance is 60 Ω, while the average turn-on voltages is 1.6 V. It was also found that temperature coefficient of these RCLEDs was about 0.11 nm/°C.     

Enhanced hydrogen production over CdSe QD/ZTP composite under visible light irradiation without using co-catalyst

A series of CdSe quantum dot (QD)/zirconium titanium phosphate (ZTP) was synthesized by solvothermal method using ethylene diamine by varying Cd to Se ratio from 1:1 to 1:4 and examined as robust catalysts for hydrogen evolution under visible light irradiation without using any co-catalyst. Extensively, the structural, optical, morphological, elemental and photoresponse spectra measurement of the composite system was studied. The catalytic activity of the materials was correlated with photoluminescence spectra, band gap energy and the photosensitization effect of CdSe quantum dot. Though neat CdSe quantum dot and zirconium titanium phosphate (ZTP) exhibited photocatalytic hydrogen evolution, the composite material showed remarkable high activity. Among these, 1CdSe quantum dot/zirconium titanium phosphate (ZTP) composite showed the highest hydrogen production (905.4 μmol) within 3 h which is consistent with low photoluminescence (PL) intensity, wide band gap energy and the photosensitization effect of CdSe quantum dot.     

PbSe量子点掺杂玻璃的制备及表征

采用高温熔融法,经过两步热处理,成功制备了PbSe量子点(QD)掺杂的硅酸盐玻璃.当热处理温度为550℃、热处理时间为1～10 h时,X射线衍射(XRD)和透射电镜(TEM)测量表明,玻璃中,生成的PbSe QD平均尺寸为5～6 nm.随着热处理时间的延长(3～8 h),玻璃中生成的PbSe QD尺寸增大.近红外荧光(...     

Intermediate-band solar cells based on dilute alloys and quantum dots

This paper describes our recent developments of intermediate-band solar cells, with a focus on the use of dilute alloys and nanostructured materials such as quantum dots (QDs). The concept of"full-spectrum" solar cells and their working mechanism with various material structures based intermediate-band solar cells, including material growth, structural and chemical analysis, device modeling and testing, are presented. Finally, the progress and challenges of quantum-dot-based solar cells are discussed.     

Temperature dependence of photoluminescence of QD arrays

It is essentially important to understand the temperature dependence of the photoluminescence of multimodal quantum dot (QD) arrays for the realization of efficient photonic devices. In this paper, the dynamics processes of different density multimodal QD arrays were fitted by using the rate equation model. It is shown that, in high density QD arrays, the intensity of photoluminescence of different QD families has different temperature dependence, and the intensity of photoluminescence is quenched as the temperature increases in low density QD arrays. In high density QD arrays, as the temperature increases, the carriers will be thermally excited into the wetting layer from QDs, and then some of them will be recaptured by the big scale QDs; carrier coupling takes place between the different QD families, while in low density QD arrays, the carrier transfer between different QD families will be limited. Temperature dependence of the maximum of the ratio of photoluminescence intensity of different QD families strongly depends on the difference of thermal activation energies.