Harnessing Light with Photonic Nanowires: Fundamentals and Applications to Quantum Optics

The efficient feeding of spontaneous emission (SE) into a controlled optical mode lies at the heart of a new generation of advanced optoelectronic devices, such as low‐threshold microlasers and bright sources of quantum light. In the solid state, single‐mode emission was first demonstrated by using the Purcell effect that arises in a resonant microcavity. Recently, the need to relax the constraints inherent to such a narrow‐band approach has motivated large effort to develop structures ensuring broadband and efficient SE control. This minireview deals with fiber‐like photonic nanowires, a class of high‐index waveguides that features key assets in this context. Combining theoretical predictions and experimental results, the paper details the SE dynamics in such tiny wires. In addition, it shows how the far‐field emission of a single wire can be tailored through proper engineering of the two wire ends. As an application in the field of quantum optics, we review the realization of an ultrabright single‐photon source. This first device was based on a self‐assembled quantum dot embedded in a wire antenna realized with a top‐down fabrication process. Considering recent advances in the direct growth of tapered photonic wires, we also propose a bottom‐up fabrication route to realize a complete device. In particular, this proposal ensures the optimal 3D positioning of a single emitter inside the antenna. Finally, future research and application prospects are also reviewed.     

Visual and fluorescent detection of acetamiprid based on the inner filter effect of gold nanoparticles on ratiometric fluorescence quantum dots

In this work, we develop a simple and rapid sensing method for the visual and fluorescent detection of acetamiprid (AC) based on the inner-filter effect (IFE) of gold nanoparticles (AuNPs) on ratiometric fluorescent quantum dots (RF-QDs). The RF-QDs based dual-emission nanosensor was fabricated by assembling green emissive QDs (QDs_539 nm, λ_em = 539 nm) on the surface of red emissive QDs (QDs_661 nm, λ_em = 661 nm)-doped silica microspheres. The photoluminescence (PL) intensity of RF-QDs could be quenched by AuNPs based on IFE. Acetamiprid can adsorb on the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on RF-QDs was weakened and the PL intensity of RF-QDs was recovered accordingly. Under the optimized conditions, the PL intensity of the RF-QDs/AuNPs system was proportional to the concentration of AC in the range of 0.025–5.0 μg mL⁻¹, with a detection limit of 16.8 μg L⁻¹. The established method had been used for AC detection in environmental and agricultural samples with satisfactory results.     

Application of ZnO quantum dots dotted carbon nanotube for sensitive electrochemiluminescence immunoassay based on simply electrochemical reduced Pt/Au alloy and a disposable device

We report on a disposable microdevice suitable for sandwich-type electrochemiluminescence (ECL) detection of prostate specific antigen (PSA). The method is making use of ZnO quantum dots dotted carbon nanotube (ZnO@CNT) and simply electrochemical reduced Pt/Au alloy. The latter was selected as immunosensing probe to modify screen-printed carbon electrode, due to its excellent electrical property. For further ultrasensitive, low-potential and stable ECL detection, ZnO@CNT composite was first synthesized using a facile solvothermal method, and employed as signal amplification label. In this work, two working electrodes in one device were used for one determination to obtain more exact results based on screen-print technique. Taking advantage of dual-amplification effects of the Pt/Au and ZnO@CNT, this immunosensor could detect the PSA quantitatively, in the range of 0.001–500 ng mL⁻¹, with a low detection limit of 0.61 pg mL⁻¹. The resulting versatile immunosensor possesses high sensitivity, satisfactory reproducibility and regeneration. This simple and specific strategy has vast potential to be used in other biological assays.     

In situ formation of p–n junction: A novel principle for photoelectrochemical sensor and its application for mercury(II) ion detection

The discovery and development of photoelectrochemical sensors with novel principles are of great significance to realize sensitive and low-cost detection. In this paper, a new photoelectrochemial sensor based on the in situ formation of p–n junction was designed and used for the accurate determination of mercury(II) ions. Cysteine-capped ZnS quantum dots (QDs) was assembled on the surface of indium tin oxide (ITO) electrode based on the electrostatic interaction between Poly(diallyldimethylammonium chloride) (PDDA) and Cys-capped ZnS QDs. The in situ formation of HgS, a p-type semiconductor, on the surface of ZnS facilitated the charge carrier transport and promoted electron-hole separation, triggered an obviously enhanced anodic photocurrent of Cys-capped ZnS QDs. The formation of p–n junction was confirmed by P–N conductive type discriminator measurements and current–voltage (I–V) curves. The photoelectrochemical method was used for the sensing of trace mercuric (II) ions with a linear concentration of 0.01 to 10.0 µM and a detection limit of 4.6 × 10⁻⁹ mol/L. It is expected that the present study can serve as a foundation to the application of p–n heterojunction to photoelectrochemical sensors and it might be easily extended to more exciting sensing systems by photoelectrochemistry.     

ZnO/CdS量子点的制备及其荧光性能

研究了用液相法的方法可控合成ZnO/CdS量子点,并通过调节前驱体的比例来制备不同光色的量子点,使ZnO/CdS量子点能够光色可调,成功地得到激发主峰在450-460 nm,发射主峰在600 nm左右的ZnO/CdS量子点,和蓝光复合可以得到暖白光,大大提高白光LEDs的显色性,这说明该量子点在暖白光发光二级管中具有潜在的应用价值.     

基于近红外胶体量子点阵列和光谱重构算法检测多种化学物质的方法研究

在众多化学物质检测技术手段中,红外检测技术由于具有非破坏性、灵敏度高、检测速度快、准确性好等特点,广泛应用于化工、生物医学、食品安全等领域。量子点光谱仪是使用量子点代替光栅作为分光器件,结合阵列探测器及光谱重构算法实现光谱检测的新型微型光谱仪,具有体积小、成本低等优点。为了进一步提升现有量子点光谱仪和量子点器件检测化学物质的普适性,为微小型近红外分光器件研制提供有效技术途径,以危险化学品乙醇、化学战剂模拟剂甲基膦酸二甲酯、二氯甲烷为目标物,通过将多种量子点材料与紫外固化胶混合后沉积在RGB点阵模块并固化,制备了发射光谱波段为900～1 600 nm的近红外胶体量子点阵列。采用经验模态分解方法提取输入光谱的高频信号以减小随机噪声干扰,并基于最小二乘法建立了相应光谱重构算法。实验结果表明,近红外胶体量子点阵列制备方法简单,成本低、稳定性较好。具有144条光谱通道的近红外胶体量子点阵列实现的重构光谱分辨率可以达到4.861 nm,与标准吸收光谱相比,其特征峰最小偏差仅为0.043%。因此,使用近红外胶体量子点阵列结合光谱重构算法可以实现气态、液态目标物的光谱重构和检测识别。未来,通过增加阵列数量可有效提升重构光谱的光谱分辨率;通过增加所选量子点材料,还可以实现从紫外到红外波段范围内的光谱检测;通过优化检测光路和重构算法参数提高目标物检测信噪比。     

Synthesis and characteristics of multifunctional Fe3O4-SiO2-CdS magnetic-fluorescent nanocomposites

A luminescent superparamagnetic nanocomposite with an Fe 3 O 4-SiO 2-CdS structure is synthesized.Coated with a silica shell,Fe 3 O 4 nanoparticles and CdS quantum dots (QDs) are successfully assembled together.Analysed from the test results of X-ray diffraction (XRD),transmission electron microscopy (TEM),high resolution transmission electron microscopy (HRTEM),hysteresis loop,and photoluminescence (PL) spectrum,these nanocomposites exhibit superparamagnetic and photoluminescent properties.     

Theory of light scattering from semiconductor quantum dots: Excitation frequency dependent emission dynamics

We present a microscopic model for the dynamic scattering and emission spectrum of a semiconductor quantum dot, after coherent optical excitation. We investigate the spectral properties and the emission dynamics of the different scattering and emission contributions considering a V-type semiconductor quantum dot model under resonant conditions and include the coupling to LO-phonons via higher order Born approximations. This theory helps identifying the different contributions to the spectrum via time resolved calculations.