一种简单的水热法制备油溶性PbSe量子点（英文）

本研究采用简单的水热法得到了单一形态学和小尺寸分布的油溶性Pb Se量子点。所得到的立方相Pb Se量子点颗粒呈现近球形,且平均颗粒尺寸为4.0±0.5 nm。Pb Se量子点在435 nm近紫外区域呈现出较强的和相对较窄的光致发光光谱,光谱的半高宽值约为80 nm。随着反应时间的延长和反应温度的升高,发光光谱向低能量区域移动,谱峰的半高宽也随之变大。在改变前驱体Pb/S摩尔比的条件下,发光光谱相对强度降低,光谱也发生向长波长区域移动。另外,随着反应温度和前驱体Pb/S摩尔比的改变,Pb Se量子点颗粒表面的缺陷也增多。在反应过程中,小颗粒长大成大尺寸颗粒促使Pb Se量子点的发光光谱向长波长移动,这个现象符合奥斯瓦尔德熟化定律。热力学不稳定和颗粒表面低浓度油酸包覆也造成Pb Se量子点颗粒表面产生缺陷。     

胶体量子点多色LED的设计、制备和表征

量子点LED采用胶体量子点为LED发光层,通过调节量子点的尺寸可以制作出覆盖可见以及近红外光谱的量子点LED(QD-LED),而且量子点LED器件发出的光谱范围很窄(光谱半高宽可达30 nm).为了研究不同发光颜色的QD-LED器件特性,本文采用具有523 nm和608 nm发光波长的CdSe/ZnS核壳型量子点为发光层、poly-TPD为空穴传输层、ZnO为电子传输层,制备了量子点红光和绿光LED并讨论了器件的相关特性.这些结果对量子点LED在飞机驾驶舱以及医疗器械照明方面的应用提供了参考,但要满足商业化的需求其寿命、亮度以及效率还需要进一步的提高.     

基于PEG修饰的ZnO量子点光学特性研究

采用溶胶-凝胶法制备了ZnO量子点, 并采用有机高分子试剂PEG(聚乙二醇, M_w=2000)对其表面进行修饰。借助X射线衍射分析、傅立叶红外光谱、光致发光谱和透射显微镜等测试方法, 研究了PEG表面修饰对ZnO量子点结构和光学性能的影响规律。研究表明, 混合加入的PEG聚合物能够成功地包覆在ZnO量子点表面, 但没有改变量子点的晶体结构, 经PEG表面修饰后的ZnO量子点尺寸变小, 稳定性增强, 分散更均匀。同时经PEG修饰的ZnO量子点在400~500 nm波长区域缺陷态发射峰明显减弱, 表明采用PEG来改善ZnO量子点表面缺陷结构具有良好效果。     

尺寸分布和界面混合对InAs/GaAs量子点光学性质的影响

研究了自组织生长模式(S-K modes)下量子点尺寸的不均匀分布对量子点发光性质的影响,对其光致发光峰进行了拟合计算.研究发现,量子点尺寸的不均匀分布导致了量子点发光峰的展宽以及发光峰位的红移.另一方面,后处理工艺中的退火及质子注入引起的界面混合导致了量子点PL谱发光峰的蓝移及半高宽的减小.     

CdS半导体纳米晶的生长及其光谱研究

用玻璃沉淀技术制备了含过饱和CdS的玻璃固溶体,在一定条件下晶化处理使其长出CdS量子点,并采用了X射线衍射、高分辨扫描电镜、光吸收谱和荧光发光光谱等测试手段分析其性能,结果表明经过晶化处理可以在玻璃中长出CdS量子点,尺寸大约为10～25nm,吸收谱中出现明显的红移现象,反映出量子点的量子限域效应,荧光发光图谱中可以看出量子点发光主要由带隙发光和表面缺陷态发光组成,提高热处理温度可以改善晶粒的完整性.     

有缺陷和无缺陷量子点内应变分布的比较与分析

阐述了量子点内能级结构与应变的关系,用ANSYS7．1计算了有缺陷和无缺陷两种情况下：InAs／GaAs量子点的应变分布,通过对计算结果的比较,讨论了两种情况下不同的应变分布对量子点电子结构影响的不同结果,指出有缺陷时量子点各能级的改变量都与无缺陷时不同,无缺陷时应变的作用只是使能级平行移动;有缺陷时,缺陷将使量子点内能级结构复杂化,有缺陷时发光波长和发光光谱都比无缺陷时复杂。     

CdSe胶质量子点的电致发光特性研究

采用胶体化学法合成硒化镉(CdSe)胶质量子点, 在此基础上制成了以CdSe胶质量子点为有源层, 结构为ITO/ZnS/CdSe/ZnS/Al的电致发光(EL)器件. 透射电镜测量表明量子点的尺寸为4.3 nm, 扫描电子显微镜测量ZnS薄膜和Al薄膜结果显示表面均较为平整, 由器件结构的X射线衍射分析观察到了CdSe(111)、ZnS(111)等晶面的衍射, 表明器件中包含了CdSe量子点和ZnS绝缘层材料. 光致发光谱表征胶质量子点的室温发光峰位于614 nm, 电致发光测量得到器件在室温下的发光波长位于450 ~ 850 nm, 峰值在800 nm附近. 本文对电致发光机制及其与光致发光谱的区别进行了讨论.     

ODA/TOPO质量比对CdSe量子点性能的影响

采用高温有机金相法,在非配位溶剂中用双配位体系十八胺(ODA)和三辛基氧化磷(TOPO)合成了CdSe量子点(QDs),表征了量子点的形貌,研究了双配位体系中不同ODA与TOPO质量比对CdSe量子点的尺寸分布和荧光量子效率的影响.结果表明,引入ODA后,可制备出分散性良好、形状规则、尺寸分布均匀的CdSe量子点.当ODA与TOPO的质量比为3-4时,量子点的尺寸约为3 nm,光谱半高宽(FWHM)达到最小值29 nm,其量子效率可以达到52.8%-58.1%.     

CdSe与CdSe/ZnS量子点合成及稀土掺杂

在LSS(liquid-solid-solution)多相体系中制得了CdSe、CdSe/ZnS量子点和Eu掺杂的量子点。利用TEM、XRD、PL、EDS对产物进行了表征。TEM结果显示所得的量子点形貌规则、尺寸均匀。XRD结果显示CdSe/ZnS量子点呈六方晶系。PL结果对比表明,合适厚度壳层ZnS包覆后的CdSe量子点发光效率明显提高,发光峰的半高宽有大幅度提高,并分析了所得的结果。掺杂稀土元素Eu后,CdSe(Eu)量子点在红光区域产生了新的发光峰;而CdSe(Eu)/ZnS量子点在红光区域内没有出现发光峰,并阐明了这种现象的原因。     

基于生物质烟灰的碳量子点的制备及性能

分别以河北沧州和山东日照的民居烟道灰为原料,通过酸回流法成功制备了具有良好水溶性和稳定性的碳量子点。高分辨透射电子显微镜观察表明碳量子点为球形颗粒,内核尺寸小于1 nm;傅里叶变换红外光谱仪和X-射线光电子能谱仪研究表明碳量子点表面含有羧基、羟基等有机官能团;拉曼光谱和X-射线衍射测量表明碳量子点结晶性差,内部含有大量缺陷;荧光光谱测量结果表明碳量子点发射黄色荧光,波长大于500 nm且具有较高的荧光量子产率,最高可达3. 83%。结果表明,民居烟道灰有望成为碳量子点制备的新型廉价原料,所获得的黄光发射碳量子点在生物成像等领域具有广阔的应用前景。     

Synthesis and luminescence characteristics of DHLA-capped PbSe quantum dots with biocompatibility

In this work, we report a facile aqueous route to prepare PbSe QDs with strong photoluminescent and near-infrared (NIR) emission using dihydrolipoic acid (DHLA) as the capping ligands. It was found that the synthesis parameters including the molar ratio of DHLA/Pb, the pH value and the reaction time have considerable influence on photoluminescent intensity (PL) of the PbSe QDs. The as-synthesized DHLA-capped PbSe QDs were characterized by high-resolution transmission electron microscopy (HRTEM), energy-dispersive analysis of X-ray (EDX) and X-ray diffraction (XRD), the results indicated that the QDs were about 8.0 ± 0.2 nm in size and had good monodisperse and a rock salt crystalline structure. Also, there was DHLA on the surface of QDs, which was confirmed by Fourier transform infrared (FT-IR) spectrometry. The PbSe QDs exhibited optimal PL intensity when Pb:Se:DHLA = 1:0.6:1 in weak alkaline aqueous. The as-synthesized QDs kept highly PL intensities when stored in the dark in normal air environment during the period of 60 days. In addition, the biocompatibility of these QDs was measured by hemolytic test, which indicated that DHLA-stabilized QDs are biocompatible. It is important for QDs as biomarkers in biological detection and diagnosis.     

ZnO含量对熔融法制备PbSe量子点玻璃的影响

采用高温熔融－退火法在钠硼铝硅酸盐（SiO2-B2O3-Na2O-Al2O3-ZnO-AIF3-Na2O）玻璃中生长了PbSe量子点,通过X射线衍射（XRD）、透射电镜（TEM）、光致荧光（PL）谱等研究了玻璃配料中不同ZnO含量对PbSe量子点尺寸和浓度的影响,结果表明,ZnO含量占总玻璃配料质量比约9．4％时,生成的量子点尺寸比较均匀,直径约为6．5nm,且浓度较高,PL谱强度最强,辐射峰位于1790nm,FWHM为296nm。玻璃配料中加入适量的ZnO有助于PbSe量子点的形成,减少Se元素的挥发,使玻璃中的量子点尺寸分布趋于均-化。     

Dark-red-emitting CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots: Effect of chemicals on properties

CdTe_0.5Se_0.5/Cd_0.5Zn_0.5S core/shell quantum dots (QDs) with a tunable photoluminescence (PL) range from yellow to dark red (up to a PL peak wavelength of 683 nm) were fabricated using various reaction systems. The core/shell QDs created in the reaction solution of trioctylamine (TOA) and oleic acid (OA) at 300 °C exhibited narrow PL spectra and a related low PL efficiency (38%). In contrast, the core/shell QDs prepared in the solution of 1-octadecene (ODE) and hexadecylamine (HDA) at 200 °C revealed a high PL efficiency (70%) and broad PL spectra. This phenomenon is ascribed that the precursor of Cd, reaction temperature, solvents, and ligands affected the formation process of the shell. The slow growth rate of the shell in the solution of ODE and HDA made QDs with a high PL efficiency. Metal acetate salts without reaction with HDA led to the core/shell QDs with a broad size distribution.     

Tuning the band gap of PbSe quantum dots in glasses by TiO doping

Titanium monoxide (TiO) was added to host glass, which was heat-treated at 520 °C for 10 h to incorporate Ti²⁺ into PbSe quantum dots (QDs) to control their band gaps. Incorporation of Ti²⁺ ions into PbSe QDs was confirmed using electron energy loss spectroscopy analysis. Addition of TiO caused blue-shift of the absorption and photoluminescence (PL) bands of the QDs. Absorption bands moved from 1621 nm at TiO concentration [TiO] = 0.0% to 1418 nm at [TiO] = 0.4 mol%. Average diameters of QDs remained mostly unaffected (i.e., 6.25 ± 0.14 nm at [TiO] = 0.0% to 6.03 ± 0.1 nm at [TiO] = 0.4 mol%). The changes in absorption and PL bands originated from the incorporation of Ti²⁺ ions into PbSe QDs. Band gaps of PbSe QDs increased from 0.76 eV at [TiO] = 0% to 0.88 eV at [TiO] = 0.4 mol%. This simple method to tune the band gap of PbSe QDs has possible applications in optical communication fiber amplifiers, infrared laser sources and saturable absorbers.     

Low-temperature noninjection approach to homogeneously-alloyed PbSe(x)S(1-x) colloidal nanocrystals for photovoltaic applications

Homogeneously alloyed PbSe(x)S(1-x) nanocrystals (NCs) with their excitonic absorption peaks in wavelength shorter than 1200 nm were developed for photovoltaic (PV) applications. Schottky-type solar cells fabricated with our PbSe?.?S?.? NCs as their active materials reached a high power conversion efficiency (PCE) of 3.44%, with an open circuit voltage (V(oc)) of 0.49 V, short circuit photocurrent (J(sc)) of 13.09 mA/cm2, and fill factor (FF) of 0.54 under Air Mass 1.5 global (AM 1.5G) irradiation of 100 mW/cm2. The syntheses of the small-sized colloidal PbSe(x)S(1-x) NCs were carried out at low temperature (60 °C) with long growth periods (such as 45 min) via a one-pot noninjection-based approach in 1-octadecene (ODE), featuring high reaction yield, high product quality, and high synthetic reproducibility. This low-temperature approach employed Pb(oleate)? as a Pb precursor and air-stable low-cost thioacetamide (TAA) as a S source instead of air-sensitive high-cost bis(trimethylsilyl)sulfide ((TMS)?S), with n-tributylphosphine selenide (TBPSe) as a Se precursor instead of n-trioctylphosphine selenide (TOPSe). The reactivity difference of TOPSe made from commercial TOP 90% and TBPSe made from commercial TBP 97% and TBP 99% was addressed with in situ observation of the temporal evolution of NC absorption and with 31P nuclear magnetic resonance (NMR). Furthermore, the addition of a strong reducing/nucleation agent diphenylphosphine (DPP) promoted the reactivity of the Pb precursor through the formation of a Pb-P complex, which is much more reactive than Pb(oleate)?. Thus, the reactivity of TBPSe was increased more than that of TAA. The larger the DPP-to-Pb feed molar ratio, the more the Pb-P complex, the higher the Se amount in the resulting homogeneously alloyed PbSe(x)S(1-x) NCs. Therefore, the use of DPP allowed reactivity match of the Se and S precursors and led to sizable nucleation at low temperature so that long growth periods became feasible. The present study brings insight into the formation mechanism of monomers, nucleation/growth of colloidal composition-tunable NCs, and materials design and synthesis for next-generation low-cost and high-efficiency solar cells.     

Synthesis and characterization of PbSe nanoparticles obtained by a colloidal route using Extran as a surfactant at low temperature

Lead selenide nanoparticles (PbSe NPs) have been obtained through an easy and low cost route using colloidal synthesis in aqueous solution. The synthesis was carried out at room temperature using Extran (Na?P?O??, NaOH and H?O) as surfactant. Hydrochloric acid (HCl) was used to eliminate the generated by-products. The size of PbSe NPs was varied by changing the Pb:Se molar concentration. The PbSe NPs were characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The XRD measurements showed that the PbSe NPs have the face-centered cubic phase structure. The crystal size was found to be between 14 and 20 nm as calculated from the XRD patterns and these values were corroborated with SEM and TEM. Additionally, HRTEM micrographs showed crystalline planes at (200), (220) and (111) of the PbSe NPs, in agreement with the XRD results.     

超高真空化学气相淀积自组织生长锗量子点

采用超高真空化学气相淀积系统制备了小尺寸、高密度、纵向自对准的Ge量子点．通过TEM和AFM对埋层和上层量子点的形貌和尺寸分布进行了研究，对生长的温度和时间进行了优化．采用硼预淀积的方法得到了尺寸分布小于3％的均匀的圆顶形Ge量子点．采用低温光荧光测量了多层量子点的光学特性．在10K的PL谱可以观察到明显的蓝移现象，表明量子点中较强的量子限制效应．量子点非声子峰的半高宽约为46meV，表明采用UHV／CVD工艺生长的多层量子点具有较窄的尺寸分布．     

Aqueous CdPbS quantum dots for near-infrared imaging

Quantum dots (QDs) are semiconducting nanocrystals that have photoluminescent (PL) properties brighter than fluorescent molecules and do not photo-bleach, ideal for in vivo imaging of diseased tissues or monitoring of biological processes. Near-infrared (NIR) fluorescent light within the window of 700-1000 nm, which is separated from the major absorption peaks of hemoglobin and water, has the potential to be detected several millimeters under the surface with minimal interference from tissue autofluorescence. Here we report the synthesis and bioimaging demonstration of a new NIR QDs system, namely, CdPbS, made by an aqueous approach with 3-mercaptopropionic acid (MPA) as the capping molecule. The aqueous-synthesized, MPA-capped CdPbS QDs exhibited an NIR emission in the range of 800-950 nm with x(i) ≥ 0.3, where x(i) denotes the initial Pb molar fraction during the synthesis. Optimal PL performance of the CdPbS QDs occurred at x(i) = 0.7, which was about 4 nm in size as determined by transmission electron microscopy, had a rock salt structure and a quantum yield of 12%. Imaging of CdPbS QDs was tested in membrane staining and transfection studies. Cells transfected with CdPbS QDs were shown to be visible underneath a slab of chicken muscle tissue of up to 0.7 mm in thickness without the use of multiple-photon microscopy.     

Deep Red Emissive Carbonized Polymer Dots with Unprecedented Narrow Full Width at Half Maximum

Development of high-performance carbon dots (CDs) with emission wavelength longer than 660 nm (deep red emission) is critical in deep-tissue bioimaging, yet it is still a major challenge to obtain CDs with both narrow full width at half maximum (FWHM) and high deep red/near-infrared emission yield. Here, deep red emissive carbonized polymer dots (CPDs) with unprecedented FWHM of 20 nm are synthesized. The purified CPDs in dimethyl sulfoxide (DMSO) solution possess quantum yield (QY) as high as 59% under 413 nm excitation, as well as recorded QY of 31% under 660 nm excitation in the deep red fluorescent window. Detailed characterizations identify that CPDs have unique polymer characteristics, consisting of carbon cores and the shells of polymer chains, and π conjugated system formed with N heterocycles and aromatic rings governs the single photoluminescence (PL) center, which is responsible for high QY in deep red emissive CPDs with narrow FWHM. The CPDs exhibit strong absorption and emission in the deep red light region, low toxicity, and good biocompatibility, making them an efficient probe for both one-photon and two-photon bioimaging. CPDs are rapidly excreted via the kidney system and hepatobiliary system.     

Aspects of emission variation in CdSeTe/ZnS quantum dots conjugated to antibodies

CdSeTe/ZnS quantum dots (QDs) with the emission peak at 705 nm have been studied comparatively in the non-conjugated state and after bioconjugation to anti-pseudo rabies virus antibodies (ABs) by means of photoluminescence (PL) and Raman scattering methods. It is revealed that PL spectra of QDs vary significantly after conjugating to ABs. In PL spectra of non-conjugated QDs only one PL band of Gaussian shape peaked at 1.76–1.78 eV and related to exciton emission in the CdSeTe core has been detected. The PL spectra of bio-conjugated QDs demonstrate the high energy spectral shift and asymmetric shape of PL bands. The study of Raman scattering spectra permits to estimate the CdSeTe alloy composition and to detect the surface enhanced Raman scattering (SERS) effect for bioconjugated QDs. The last fact testifies on the interaction of excitation light electromagnetic field with the electric dipoles excited in ABs. The optical band gap in CdSeTe core has been calculated numerically versus core radius on the base of the effective mass approximation model. Then the energy band diagrams for non-conjugated and bio-conjugated states of CdSeTe/ZnS QDs have been designed. It is revealed the type II quantum well in CdSeTe core that explains the optical transition at 705 nm in the wide band gap CdSeTe alloy. The analysis has shown that AB dipoles excited in bio-conjugated QDs stimulate changing the profile of QD energy band diagram that manifests itself in the mentioned PL spectrum transformations. Actually, the study of PL spectrum varying in CdSeTe/ZnS QDs conjugated to specific antibodies can be an informative tool in biology and medicine for early medical diagnostics.