Ultrafast Carrier Dynamics in CdSe/CdS/ZnS Quantum Dots

The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.

Effect of gamma irradiation on optical properties of CdSe/ZnS quantum dots embedded in PDMS

The optical properties of CdSe/ZnS quantum dots(QDs)embedded in polydimethylsiloxane(PDMS)flexible materials after irradiated withγ-rays were studied.As an embedding matrix,PDMS exhibits the advantage of high radiation hardness.The luminescence spectra and fluorescence lifetime of the irradiated and unirradiated samples were tested.The fluorescence intensity of QDs decreases with the increase of the irradiation dose according to the result of luminescence spectra.The fluorescence intensity of the QDs decreases by 80%after irradiation with a dose of 1 kGy,but the position of the emission peak and the spectral shape of the QDs remain consistent before and after irradiation.In addition,the fluorescence lifetime of QDs is shortened after irradiation.Based on the fluorescence response of QDs to the irradiation ofγ-rays and combined with flexible materials,our work provides a theoretical basis for the application of QDs as a new wearable dosimeter.

Uniform-dispersed ZnS quantum dots loading on graphene as a promising anode for potassium-ion batteries

The potassium-ion batteries(PIBs)have become the promising energy storage devices due to their relatively moderate cost and plenteous potassium resources.Whereas,the main drawback of PIBs is unsatisfacto ry electrochemical perfo rmance induced by the larger ionic radius of potassium ion.Herein,we report a well-designed,uniform-dispersed,and morphology-controllable zinc sulfide(ZnS)quantum dots loading on graphene as an anode in the PIBs.The directed uniform dispersion of the in-situ growing ZnS quantum dots(~2.8 nm in size)on graphene can mitigate the volume effect during the insertionextraction process and shorten the migration path of potassium ions.As a result,the battery exhibits superior cycling stability(350.4 mAh/g over 200 cycles at 0.1 A/g)and rate performance(98.8 mAh/g at2.0 A/g).We believe the design of active material with quantum dot-minimized size provides a novel route into PIBs and contributes to eliminating the major electrode failure issues of the system.

Synthesis of bovine serum albumin imprinted Mn:ZnS quantum dots

A novel bovine serum albumin （BSA） imprinted Mn-doped ZnS quantum dots （Mn：ZnS QDs） is firstly reported. The molecular imprinted polymer （MIP） functionalized Mn：ZnS QDs （Mn：ZnS @SiO2@MIP） include the preparation of Mn：ZnS QDs, the coating of silica on the surface of Mn：ZnS QDs, and the functional polymerization by sol-gel reaction using 3-aminophenylboronic acid as the functional and cross-linking monomer in the presence of BSA （Mn：ZnS@SiO2@MIP-BSA）, and then the elution of the imprinted BSA on the surface of Mn：ZnS@SiO2 QDs. The results showed that the phosphorescence of Mn：ZnS@SiO2@MIP is stronger quenched by BSA than that of non-imprinted one （Mn：ZnS@SiO2@NIP）, indicating that the selectivity of the imprinted Mn：ZnS quantum dots toward BSA is superior to that of non-imprinted one.

Enhanced chemiluminescence from reactions between CdTe/CdS/ZnS quantum dots and periodate

A novel chemiluminescence（CL） performance of CdTe/CdS/ZnS quantum dots（QDs） with periodate（KIO_4） was studied.Effects of concentration and pH on the CL system were investigated.Electron spin resonance（ESR） and the effects of radical scavenger analysis were employed for identification of intermediate species.The CL spectra for this system showed only one maximum emission peak centered around 620 nm,which was similar with photoluminescence（PL） spectra of CdTe/CdS/ZnS QDs.The CL of CdTe/CdS/ZnS QDs was induced by direct chemical oxidation and the possible mechanism could be explained by radiative recombination of injected holes and electrons.This investigation not only provided new sight into the optical characteristics of CdTe/CdS/ZnS QDs,but also broadened their potential optical utilizations.

AgInS_(2)/ZnS quantum dots for noninvasive cervical cancer screening with intracellular pH sensing using fluorescence lifetime imaging microscopy

Intracellular pH plays a critical role in biological functions,and abnormal pH values are related to various diseases.Here,we report on an intracellular pH sensor AgInS_(2)(AIS)/ZnS quantum dots(QDs)that show long fluorescence lifetimes of hundreds of nanoseconds and low toxicity.Fluorescence lifetime imaging microscopy(FLIM)combined with AIS/ZnS QDs is used for the imaging of live cells in different pH buffers and different cell lines.The FLIM images of AIS/ZnS QDs in live cells demonstrate different intracellular pH values in different regions,such as in lysosomes or cytoplasm.This method can also distinguish cancer cells from normal cells,and the fluorescence lifetime difference of the AIS/ZnS QDs between the two types of cells is 100±7 ns.Most importantly,the exfoliated cervical cells from 20 patients are investigated using FLIM combined with AIS/ZnS QDs.The lifetime difference value between the normal and cervical cancer(CC)groups is 115±9 ns,and the difference between the normal and the precancerous lesion group is 64±9 ns.For the first time,the noninvasive method has been used for cervical cancer screening,and it has shown great improvement in sensitivity compared with a clinical conventional cytology examination.

Enzymatic detection of ethanol based on H_2O_2-sensitive quantum dots

A rapid and sensitive fluorometric method for the enzymatic detection of ethanol using CdSe/ZnS quantum dots （QDs） is proposed. The photoluminescence of QDs is sensitive to H202. This finding leads to a novel approach for the determination of ethanol using alcohol oxidase （AOx） which, on oxidation of ethanol, produces H202. The method has higher sensitivity, wider analytical range （0.1-8 mmol/L）, and a lower detection limit （0.05 mmol/L）. The relationship between quenching of the photoluminescence of the QDs and the concentration of ethanol is linear.

InP/ZnS QDs对稀有鮈鲫子代软骨发育的影响

使用InP/ZnS QDs以雌性稀有鮈鲫(Gobiocypris rarus)为实验动物,通过腹腔注射染毒,设计了(200,400,800nmol/L)3个实验组,在量子点暴露4和7d时取卵受精.以胚胎受精率、存活率、仔鱼体长、全长为指标,对仔鱼进行阿利新蓝染色和HE(Hematoxylin Eosin)染色,通过检测发育相关基因(bmp2b,sox9a,runx_(2)b)的相对表达量,研究InP/ZnS QDs对稀有鮈鲫子代软骨发育的影响.结果表明:高浓度组仔鱼的体长减少6.2%、全长减少5.9%;颅面PQ-Meckel角增加24.8%,下颌骨长度减小14.6%和15.2%、宽度减小10.0%和10.7%;颅面软骨细胞肿大、数量减少.并发现QDs在不同发育时间对相关基因的相对表达量影响不同.总之InP/ZnS QDs会对稀有鮈鲫子代软骨发育产生不良影响.

The Electrochemical Behavior of Au/Au NPs/PNA/ZnS e-QD/ACA Electrode Towards Cy SH Oxidation

This work describes the electrochemical behavior of azodicarboxamide(ACA) film immobilized on the surface of penicillamine(PNA)/Zn Se-quantum dot(Zn Se-QD) gold nanoparticle(Au NPs) Au electrode. Electrocatalytic activity of modified electrode toward the oxidation of cysteine(Cy SH) was investigated. The surface structure and composition of the sensor were characterized by scanning electron microscopy(SEM). Oxidation of Cy SH on the surface of modified electrode was investigated with cyclic voltammetry, electrochemical impedance spectroscopy(EIS),hydrodynamic voltammetry and chronoamperometry methods. The results show that the PNA/Zn Se-QD/ACA film displays excellent electrochemical catalytic activities towards Cy SH oxidation. The modified electrode shows reproducible behavior and high level of stability during the electrochemical experiments. Also it has short response time, low detection limit, high sensitivity and low operation potential, which can be used as an amperometric sensor for monitoring of Cy SH. The proposed modified electrode was successfully used for determination of Cy SH in real sample such as human serum.

Identification of cadmium containing metabolites in HepG2 cells after treatment with cadmium-selenium quantum dots

The transformation of quantum dots(QDs)by organisms has attracted broad attention but remains unclear.Understanding of the metabolites helps to reveal the transformation pathway of QDs.Cd containingmetallothionein(MT)are the main species formed by Cd released from CdSe QDs in HepG2 cells,while speciation analysis of Cd containing MTs remains a challenge because MTs has several subisoforms and can bind with several metals.Herein,we built a hyphenated platform for speciation analysis of QDs in HepG2 cells after treatment with CdSe/ZnS QDs.The Cd-containing MTs were separated in reversed phase high performance liquid chromatography(RP-HPLC)and subsequently online detected by inductively coupled plasma mass spectrometry(ICP-MS)and electrospray ionization quadrupole time-of-flight mass spectrometry(ESI-Q-TOF-MS)parallelly.Four groups of Cd-containing metabolites were found by detecting Cd in ICP-MS.Their structures were identified in ESI-Q-TOF-MS and further confirmed with standards of four subisoforms of MT,including N-terminal acetylation MT2a,N-terminal acetylation MT1e,N-terminal acetylation MT1g and MT1m.Each group of them contains various stoichiometry of Cd/Zn.The metabolites of QDs remain same while the concentrations of each metabolite and its stoichiometry of Cd/Zn vary for different incubation concentration/time.This work provides a new parallel hyphenation technique of HPLC-ICP-MS/ESI-MS with high separation resolution and powerful detection ability,and the obtained results provide detailed metabolism information of QDs in HepG2 cells after treatment of CdSe/ZnS QDs,contributing to deep exploration of the functional mechanisms of QDs in organisms.

Improved performance of CdSe/ZnS quantum dot light-emitting diodes through doping with small molecule CBP

The poor film formation of Cd Se/Zn S quantum dots(QDs) during spin-coating makes a substantial impact on the device performance of quantum dot light-emitting diodes(QLEDs). This work proposes a method to improve the morphology of the quantum dot light-emitting layer(EML) by adding small organic molecular 4,4'-Bis(9 H-carbazol-9-yl) biphenyl(CBP) into the layer. Its surface roughness reduces from 6.21 nm to 2.71 nm, which guarantees a good contact between hole transport layer(HTL) and EML. Consequently, the Cd Se/Zn S QDs:CBP based QLED achieves maximum external quantum efficiency(EQE) of 5.86%, and maximum brightness of 10 363 cd/m^(2). It is demonstrated that the additive of small organic molecules could be an effective way to improve the brightness and the efficiency of QLEDs.

Novel ultra-wideband fluorescence material:Defect state control based on nickel-doped semiconductor QDs embedded in inorganic glasses

In recent years,the development of an environmentally friendly quantum dots(QDs)embedded luminous solid by a simple method has attracted considerable attention.In this study,semiconductor ZnS QDs were successfully prepared in an inorganic matrix of amorphous glass,which yielded beneficial broadband emission in the long-wavelength region of the visible range.The strong red emission belonged to the defect state energy level of the ZnS QDs,which could be enhanced by incorporation of nickel ions into the fixed matrix to regulate the defects state.The novel material had a small self-absorption,wide excitation and emission ranges,and thus potential applications in light-conversion devices,luminescent solar concentrators,and solar cell cover glasses.

Multiplexed Detection of Fe^(3+), Cobalamin and Folate Using Fluorescent Nanoprobe-Based Microarrays and a Smartphone

This work reports on a smartphone-based quantitative POCT system which consists of a paper-based microarray chip,a homemade LEGO dark-box,and a smartphone installed with custom-designed FChip-APP,for on-site quantitation of Fe^(3+),Vitamin 12(VB12),and folic acid(FA).Collection and automatic analysis of fluorescence turn-off response of three kinds of fluorescent nanoprobes which are coated onto filter papers by a smartphone-based device is the principle behind this study.The POCT system exhibits good analytical performance for multiplexed analysis of Fe^(3+),VB_(12)and FA with a wide linear range(Fe^(3+),1.0–14.0μg mL^(-1)(R^(2)=0.983);VB_(12),1.35–40.0μg mL^(-1)(R^(2)=0.991);FA,2.0–26.0μg mL^(-1)(R^(2)=0.994))and low detection limit(Fe^(3+),0.35μg mL^(-1);VB12,0.47μg mL^(-1);FA,0.56μg mL^(-1)).The cost and weight of the whole system are~$220 and~600 g per set,highlighting its cost-eff ectiveness and portability.The simple operation procedures and user-friendly interface of the FChip-APP validate the ease-of-use feature of the reported system.This versatile smartphonebased quantitative POCT system provides a cost-eff ective and easy-of-use method for screening the context-specific causes of anemia and thus its eff ective interventions in the future,especially in resource-limited areas.