Enhanced transient photovoltaic characteristics of core–shell ZnSe/ZnS/L-Cys quantum-dot-sensitized TiO_2 thin-film

Photoanodic properties greatly determine the overall performance of quantum-dot-sensitized solar cells（QDSCs）. In the present report, the microdynamic behaviors of carriers in the nanocomposite thin-film, a Zn Se QD-sensitized mesoporous La-doped nano-TiO2 thin-film, as a potential candidate for photoanode, are probed via nanosecond transient photovoltaic（TPV） spectroscopy. The results confirm that the L-Cys ligand has a dual function serving as a stabilizer and molecular linker. Large quantities of interface states are located at the energy level with a photoelectric threshold of1.58 eV and a quantum well（QW） depth of 0.67 eV. This QW depth is approximately 0.14 eV deeper than the depth of QW buried in the Zn Se QDs, and a deeper QW results in a higher quantum confinement energy. A strong quantum confinement effect of the interface state may be responsible for the excellent TPV characteristics of the photoanode. For example, the peak intensity of the TPV response of the QD-sensitized thin-film lasts a long time, from 9.40 × 10^（-7） s to 2.96 × 10^（-4） s,and the end time of the PTV response of the QD-sensitized thin-film is extended by approximately an order of magnitude compared with those of the TiO2 substrate and the QDs. The TPV characteristics of the QD-sensitized thin-film change from p-type to n-type for the QDs before and after sensitizing. These properties strongly depend on the extended diffusion length of the photogenerated carries and the reduced recombination rate of photogenerated electron-hole pairs, resulting in prolonged carrier lifetime and an increased level of electron injection into the TiO2 thin-film substrate.

Rational design of AgGaS/ZnS/ZnS quantum dots with a near-unity photoluminescence quantum yield via double shelling scheme

In this study,a two-step method was used to synthesize highly luminescent AgGaS/ZnS/ZnS quantum dots(QDs).In the first step,an inner ZnS shell was formed via a one-pot method,which resulted in a smaller lattice mismatch between the AgGaS core and the outer ZnS shell,thereby facilitating the formation of a thick outer shell.After the two-step shelling process,the synthesized AgGaS/ZnS/ZnS QDs showed an excellent photoluminescence quantum yield(PLQY)of 96.4%with a peak wavelength of 508 nm,repre-senting the highest PLQY reported thus far for AgGaS QDs.Furthermore,the effect of halogen ions in Zn precursors on the shelling process was investigated.It was proposed that the capacity of halogen ions to coordinate with the QDs influenced the balance between Zn cation diffusion and ZnS shelling reaction.Specifically,the ZnS shelling reaction was dominant when ZnCl_(2)was employed,while Zn cation diffusion was the dominant process under the I^(−)-rich environment.This work provides insights into the interfacial restructuring during the ZnS shelling and offers a clear map for the tailored synthesis of core/shell QDs.

Infrared light-emitting diodes based on colloidal Pb Se/Pb S core/shell nanocrystals

Colloidal Pb Se nanocrystals(NCs)have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ranges.However,the fast degradation of colloidal Pb Se NCs in ambient conditions hampers their widespread applications in infrared optoelectronics.It is well-known that the inorganic thick-shell over core improves the stability of NCs.Here,we present the synthesis of Pb Se/Pb S core/shell NCs showing wide spectral tunability,in which the molar ratio of lead(Pb)and sulfur(S)precursors,and the concentration of sulfur and Pb Se NCs in solvent have a significant effect on the efficient Pb S shell growth.The infrared light-emitting diodes(IR-LEDs)fabricated with the Pb Se/Pb S core/shell NCs exhibit an external quantum efficiency(EQE)of 1.3%at 1280 nm.The ligand exchange to optimize the distance between NCs and chloride treatment are important processes for achieving high performance on Pb Se/Pb S NC-LEDs.Our results provide evidence for the promising potential of Pb Se/Pb S NCs over the wide range of infrared optoelectronic applications.

The Magnetic Field Effects on Radially Symmetric Core-Shell-Shell Structure

In this paper, we modeled a core/shell/shell structure with cylindrical Schrodinger-Poisson coupled equation when a magnetic field is (and is not) applied along its axis. We showed the electron density is peaked near the outer surface of the channel when the magnetic field is applied. Therefore one may make a nano-device which its electrons move only on its outer surface. Also we applied a gate voltage to the device and showed a higher threshold voltage (to turn on the device) is necessary when a magnetic field is applied. This is because of the increase in the lowest energy level similar to the size quantization. i.e a device with longer channel looks like a device with shorter channel if it is placed in a magnetic field parallel to its axis.

ZnSe基蓝光量子点的中间壳层结构调控及其发光性能研究

ZnSe作为一种不含重金属的宽带隙量子点(QDs),近年来在蓝光量子点及其发光二极管器件领域受到广泛关注。然而,ZnSe基核壳结构蓝光量子点的核壳界面处通常存在较大的晶格失配,易于形成缺陷态捕获载流子,从而影响其光学性能。本文通过将均质的单层ZnSeS合金层替换为具有组分渐变结构的ZnSeS合金层,合成了具有径向方向Se/S浓度渐变梯度的ZnSeS合金中间壳层的ZnSeTe/ZnSe/ZnSeS/ZnS量子点,并利用X射线衍射谱、稳态光致发光光谱、时间分辨发光光谱、透射电镜和电致发光测试等表征手段研究了不同合金中间壳层对量子点结构、形貌和光学性能的影响。结果表明,所合成的具有组分梯度ZnSeS壳层的量子点的发射波长均为深蓝色(444.5 nm),发射线宽窄(<18 nm),尺寸均一,具有闪锌矿结构,结晶度高;随着ZnSeS合金中间壳层沿量子点径向方向组分渐变平滑度的不断提高,量子点的荧光量子效率(PLQY)和色纯度等光学性质依次改善,其中通过S原子扩散形成的具有线性缓变ZnSeS壳层的量子点具有最窄的发射线宽(15.8 nm)和最高的PLQY(20.7%)。利用这种具有最优荧光性能的量子点作为发光材料制备的发光二极管器件的最大外量子效率为1.8%,最高亮度为750 cd/m^(2)。本研究提出的量子点合成方案和结构优化策略有助于促进高质量无毒蓝光ZnSe基核/壳量子点的发展。

壳层厚度调控对AgIn_(x)Ga_(1-x)S_(2)/AgGaS_(2)量子点发光性能的影响

采用多次交替注入壳层前驱体工艺,成功制备了具有不同壳层厚度的环保型AgIn_(x)Ga_(1-x)S(2)/AgGaS_(2)(AIGS/AGS)量子点。利用透射电子显微镜和X射线衍射技术对量子点的形貌及晶体结构进行了详细的表征,通过吸收光谱和光致发光光谱系统地分析了AGS壳层厚度对AIGS/AGS量子点发光性能的影响。实验结果表明,适当增加AGS壳层可以有效增强量子点的带边发射,抑制其缺陷发射,并显著提高其发光稳定性。经优化,具有最佳壳层厚度(5层)的AIGS/AGS量子点呈现出532 nm的纯正绿色发光和33 nm的半高全宽(FWHM),光致发光效率(PLQY)达到45%。将其应用于量子点发光二极管(QLED)的制备,所得器件的最大亮度可达1518 cd/m^(2),外量子效率(EQE)为0.26%,显示出良好的应用潜力。

压电椭圆柱形InAs/InP核/壳量子点中杂质态线性和非线性光学性质

在有效质量近似下,考虑压电场的影响,利用微扰法研究了闪锌矿和纤锌矿InAs/InP压电核/壳椭圆柱形量子点的一阶线性、三阶非线性以及总的光学吸收系数和折射率在不同核尺寸、杂质位置及椭圆率下的变化。结果表明:壳尺寸及杂质位置固定时,随着核尺寸的增大,吸收系数及折射率的峰值位置都出现红移现象,并且峰值强度增大;当杂质位置在径向ρ0变化时,随着ρ0的增大,吸收系数及折射率的峰值位置出现红移,伴随着峰值强度增加;随着椭圆率的增大,除杂质在量子点中心处,吸收系数和折射率的峰值位置发生明显蓝移,伴随着峰值强度出现不同程度的增加。当杂质位置在轴向z 0变化时,由于压电场和量子限域效应的综合影响,与z_(0)=-0.5 H时(H为量子点沿z轴的量子限域高度)相比,z_(0)=0,0.5 H时的吸收系数及折射率的峰值位置发生不同程度的蓝移。此外,与纤锌矿结构相比,闪锌矿结构中体系的吸收系数和折射率峰值位置整体发生较大的蓝移。

界面电子结构对核壳量子点/聚乙烯纳米复合绝缘电导与空间电荷特性的影响

为研究核壳量子点的界面电子结构对聚乙烯绝缘电导与空间电荷特性的影响,分别制备了CdSe@ZnS/LDPE,ZnSe@ZnS/LDPE两种核壳量子点纳米复合绝缘,研究了复合绝缘的直流电导和空间电荷的演变规律,并分析了核壳量子点的界面电子结构对电荷陷阱分布特性的影响机理.研究发现,相比于LDPE绝缘,ZnSe@ZnS/LDPE复合绝缘在高温强场条件下直流电导率可降低47.2%,空间电荷积累量降低了40.3%,且陷阱能级增大,表现出对载流子更强的捕获作用.基于密度泛函理论,计算了核壳量子点与聚乙烯绝缘的能带特征.结果表明,核壳纳米量子点的核层-壳层界面、壳层-绝缘界面的能带偏移导致导带底与价带顶发生突变,分别对电子和空穴具有限域作用,且限域效应随着量子点核层与壳层带隙差异增大而逐渐增强,从而限制高温强场下载流子迁移、抑制空间电荷积聚.

CdTe/ZnS核壳结构半导体量子点的荧光特性研究

纳米技术研究体系中量子点是重要的研究模块之一,量子点尺寸非常小,具有独特的光物理特性。该文旨通过实验进行分析,实验过程选择99%纯度硼氢化钠、99%纯度硫酸锌、S212恒速搅拌器、TG16-WS高速离心机、0.310 mL巯基乙酸等,制备0.4565 g CdCl_(2)·2.5H_(2)O混合液,当样本溶液呈现橙色时,表明CdTe核已制备完成。实验结果显示:单脉冲能量增加时,τ_(-rise)与τ_(2)有所降低,τ_(1)数值增加,τ_(-rise)与壳层厚度呈正比关系。通过对量子点荧光特性的分析,有利于促进核壳结构量子点的制备。

纯蓝光ZnSe基核/壳结构量子点的合成与发光性能

探索了纯蓝光ZnSe基核/壳结构量子点的合成方法,研究了各种反应参数对量子点发光性能的影响,通过Te元素掺杂和尺寸调控相结合的方法使量子点发光波长红移至蓝光波段,并通过引入氟化锌对表界面缺陷进行腐蚀/钝化,从而提高了所制备量子点的发光强度。结果表明,当初始反应温度为200℃、初始反应时间为120 min时,得到的ZnSe核可以实现380 nm波长的发光,且更加适合后续的Te元素掺杂;当Te和Se的摩尔比为0.01时,所合成的ZnSe基核/壳量子点在实现442 nm波长的蓝色发光的同时,保持了15 nm的窄发光半峰全宽;当ZnF_(2)的添加量为1.5 mmol时,量子点的发光强度比不添加ZnF_(2)时提升了约3倍;量子点尺寸均一且在正辛烷中保持了高分散性,具有良好的成膜性,所制备出的量子点薄膜表面致密平滑无明显裂纹。本研究结果有助于促进高质量无毒蓝光ZnSe基核/壳量子点合成技术的发展及其在下一代显示技术中的应用。

基于核壳型量子点的生物传感器在真菌毒素检测中的应用进展

真菌毒素是真菌产生的有毒次生代谢物,其广泛存在于被污染的食物中,其中黄曲霉毒素已被认定为天然存在的剧毒致癌物。鉴于真菌毒素污染给人类健康与安全带来的风险与危害,发展低成本、快速、高效的检测方法以确保食品安全,具有重要的现实意义。已有大量研究者构建了基于单一量子点或其他荧光材料为荧光探针的生物传感器用于检测真菌毒素,并且从材料、检测方法和生物传感器等角度进行了详细的检测。然而,目前并没有系统地阐述核壳量子点构建的生物传感器在真菌毒素中的应用报道,因此,本文主要从基于核壳量子点构建的免疫电化学发光传感器、适配体免疫电化学发光传感器、免疫荧光传感器、适配体荧光传感器和试纸条传感器在真菌毒素中的应用进展进行阐述,首次系统地阐述了核壳型量子点生物传感器在真菌毒素分析检测中的研究进展,以期为同类研究提供一定的理论依据。

银锰共掺杂Zn-In-Se核壳量子点的发光性能

为了得到一种高性能的白光发光二极管用荧光材料,采用热注入法合成了一种银锰共掺杂的核/壳量子点。利用X射线衍射、透射电子显微镜、紫外-可见分光光度计、荧光光谱仪对样品的微观形貌、结构以及发光性能进行了测试与表征。测试结果表明:成功制备了目标量子点,所得样品呈类球形,平均粒径为(10.7±0.5)nm;该量子点能被紫外光有效激发,发射峰位于510 nm与615 nm处;与未包覆ZnSe壳层的量子点相比,核/壳量子点的发光强度与稳定性得到显著提升,并且量子产率达到了68%。核/壳结构量子点在254 nm紫外光连续辐照24 h后以及温度达到475 K时仍分别保持初始亮度的82%与50%。该量子点的优异发光性能与稳定性表明其在照明领域具有良好的应用前景。

Photoluminescence of Ag-In-S/ZnS quantum dots: Excitation energy dependence and low-energy electronic structure

Cd-free Ⅰ-Ⅲ-Ⅵ group semiconductor quantum dots (QDs) like Ag-ln-S and Cu-ln-S show unstructured absorption spectra with a pronounced Urbach tail,rendering the determination of their band gap energy (Eg) and the energy structure of the exciton difficult.Additionally,the origin of the broad photoluminescence (PL) band with lifetimes of several hundred nanoseconds is still debated.This encouraged us to study the excitation energy dependence (EED) of the PL maxima,PL spectral band widths,quantum yields (QYs),and decay kinetics of AlS/ZnS QDs of j different size,composition,and surface capping ligands.These results were then correlated with the second derivatives of the corresponding absorption spectra.The excellent match between the onset of changes in PL band position and spectral width with the minima found for the second derivatives of the absorption spectra underlines the potential of the EED approach for deriving Eg values of these ternary QDs from PL data.The PL QY is,however,independent of excitation energy in the energy range studied.From the EED of the PL features of the AlS/ZnS QDs we could also derive a mechanism of the formation of the low-energy electronic structure.This was additionally confirmed by a comparison of the EED of PL data of as-synthesized and size-selected QD ensembles and the comparison of these PL data with PL spectra of single QDs.These results indicate a strong contribution of intrinsic inhomogeneous PL broadening to the overall emission features of AlS/ZnS QDs originating from radiative transitions from a set of energy states of defects localized at different positions within the quantum dot volume,in addition to contributions from dimensional and chemical broadening.This mechanism was confirmed by numerically modelling the absorption and PL energies with a simple mass approximation for spherical QDs and a modified donor-acceptor model,thereby utilizing the advantages of previously proposed PL mechanisms of ternary QDs.These findings will pave the road to a deeper understanding of the nature of PL in quantum confined Ⅰ-Ⅲ-Ⅵ group semiconductor nanomaterials.

A perspective on functionalizing colloidal quantum dots with DNA

This perspective provides an overview of the techniques that have been developed for the conjugation of DNA to colloidal quantum dots （QDs）, or semiconductor nanocrystals. Methods described include： ligand exchange at the QD surface, covalent conjugation of DNA to the QD surface ligands, and one-step DNA functionalization on core QDs or during core/shell QD synthesis in aqueous solution, with an emphasis on tile most recent progress in our lab. We will also discuss emerging trends in DNA-functionalized QDs for potential applications.

Rationally designed synthesis of bright AgInS2/ZnS quantum dots with emission control

In the blossoming field of Cd-free semiconductor quantum dots(QDs),ternary Ⅰ-Ⅲ-VI QDs have received increasing attention due to the ease of the environmentally friendly synthesis of high-quality materials in water,their high photoluminescence(PL)quantum yields(QYs)in the red and near infrared(NIR)region,and their inherently low toxicity.Moreover,their oxygen-insensitive long PL lifetimes of up to several hundreds of nanoseconds close a gap for applications exploiting the compound-specific parameter PL lifetime.To overcome the lack of reproducible synthetic methodologies and to enable a design-based control of their PL properties,we assessed and modelled the synthesis of high-quality MPA-capped AglnS2/ZnS(AlS/ZnS)QDs.Systematically refined parameters included reaction time,temperature,Ag:In ratio,S:In ratio,Zn:In ratio,MPA:ln ratio,and pH using a design-of-experiment approach.Guidance for the optimization was provided by mathematical models developed for the application-relevant PL parameters,maximum PL wavelength,QY,and PL lifetime as well as the elemental composition in terms of Ag:ln:Zn ratio.With these experimental data-based models,MPA:ln and Ag:ln ratios and pH values were identified as the most important synthesis parameters for PL control and an insight into the connection of these parameters could be gained.Subsequently,the experimental conditions to synthetize QDs with tunable emission and high QY were predicted.The excellent agreement between the predicted and experimentally found PL features confirmed the reliability of our methodology for the rational design of high quality AlS/ZnS QDs with defined PL features.This approach can be straightforwardly extended to other ternary and quaternary QDs and to doped QDs.

Determination of Hydrocortisone in Cosmetics by CdSe/CdS Quantum Dots-Based Fluoroimmunoassay Using Magnetic Fe304/Au Nanoparticles as Solid Carriers

This work demonstrated the feasibility of detecting hydrocortisone in cosmetics using a novel CdSe/CdS quan- tum dots-based competitive fluoroimmunoassay with magnetic core/shell Fe3Oa/Au nanoparticles （MCFN） as solid carriers. Hydrocortisone antigen was labeled with the synthesized core/shell CdSe/CdS quantum dots （QDs） to form the antigen-QDs conjugate. Meanwhile, hydrocortisone antibody was incubated with MCFN and the immobilized antibody was obtained. The immobilized antibody was then mixed sequentially with hydrocortisone and a slightly excess amount of the QDs-labeled hydrocortisone antigen, allowing their competition for binding with the antibody immobilized on MCFN. The bound hydrocortisone and the antigen-QDs conjugates on MCFN were removed subsequently after the mixture was applied to a magnetic force. The analyte concentration was obtained by measuring the fluorescence intensity of the unbound hydrocortisone antigen-QDs conjugates. The proposed method was characterized by simplicity, rapidity, and high sensitivity with a wide linear working range of 0.5 to 15000 pg·mL^-1 and a low detection limit of 0.5 pg.mL^- 1. The proposed method was successfully applied to the determination of hydrocortisone in cosmetics with satisfactory results.

Ce^(3+)掺杂碳量子点荧光检测2,4-二硝基酚的研究

水中2,4-二硝基酚的分析检测具有重要意义。以胡麻籽壳为碳源,1-己基-3-甲基咪唑氯盐为溶剂,绿色制备了铈掺杂的碳量子点(LCQDs)。透射电镜结果表明所得LCQDs呈球状,粒径范围1~9nm。基于2,4-二硝基酚对LCQDs的特异性荧光淬灭作用建立了一种2,4-二硝基酚的荧光分析方法,最佳实验条件下,检出限为1.8μmol/L。该方法用于实际水样检测时,回收率可达94.6%~103.5%。

High-brightness green InP-based QLEDs enabled by in-situ passivating core surface with zinc myristate

The performance of red InP and blue ZnTeSe-based quantum dots(QDs)and corresponding QD light emitting diodes(QLEDs)has already been improved significantly,whose external quantum efficiencies(EQEs)and luminances have exceeded 20%and 80000 cd m-2,respectively.However,the inferior performance of the green InP-based device hinders the commercialization of full-color Cd-free QLED technology.The ease of oxidation of the highly reactive InP cores leads to high non-radiative recombination and poor photoluminescence quantum yield(PL QY)of the InP-based core/shell QDs,limiting the performance of the relevant QLEDs.Here,we proposed a fluoride-free synthesis strategy to in-situ passivate the InP cores,in which zinc myristate reacted with phosphine dangling bonds to form Zn–P protective layer and protect InP cores from the water and oxygen in the environment.The resultant InP/ZnSe/ZnS core/shell QDs demonstrated a high PL QY of 91%.The corresponding green-emitting electroluminescence devices exhibited a maximum EQE of 12.74%,along with a luminance of over 175000 cd m^(-2)and a long T50@100 cd m^(-2)lifetime of over 20000 h.

CdTe/ZnSe核壳量子点免疫层析试纸条检测克伦特罗的研究

采用巯基丁二酸作为表面修饰剂,水相法合成水溶性的CdTe/ZnSe核壳量子点,然后在N-羟基琥珀酰亚胺(NHS)的作用下,将CdTe/ZnSe核壳量子点与抗克伦特罗多克隆抗体(Anti-CLE pAb)连接。通过凝胶电泳和斑点杂交实验,验证CdTe/ZnSe核壳量子点与Anti-CLE pAb连接成功,并且CdTe/ZnSe-Anti-CLE pAb偶联物能识别克伦特罗-BSA抗原(CLE-BSA)。光谱分析表明,量子点与抗体连接后荧光增强,荧光峰位从628nm红移至635nm。将合成的CdTe/ZnSe-Anti-CLE pAb偶联物作为指示克伦特罗(CLE)分子的荧光标记物,制备出一种用于检测CLE的免疫层析试纸条,其最低检测量可达1μg/L。与ELISA法的对比实验表明,此试纸条能应用于CLE残留的快速检测。

CdTe/CdS核壳量子点与蛋白质荧光标记

利用连续离子层吸附技术合成了水溶性的CdTe/CdS核壳量子点.通过CdS壳层的包覆,量子点的量子效率由原来的15%(裸核)提高到38%(核壳),这种核壳结构量子点的化学和光学性质具有更好的稳定性,可以用于生物标记.本文采取共价连接与静电吸附两种方法,实现了量子点的生物标记,电泳技术已证明,应用这种量子点成功地实现了对蛋白质分子的生物标记.通过对量子点与蛋白质偶联前后的荧光光谱分析,发现量子点与蛋白质作用后荧光增强是由于蛋白质对量子点进行了表面修饰,从而降低了表面缺陷引起的非辐射跃迁几率所致.通过共价连接量子点的荧光峰位红移,主要是由于偶极-偶极相互作用引起的;量子点与蛋白质静电吸附作用引起的荧光峰位蓝移主要起因于量子点表面电荷量的降低.