Facile preparation of highly luminescent CdTe quantum dots within hyperbranched poly(amidoamine)s and their application in bio-imaging

A new strategy for facile preparation of highly luminescent CdTe quantum dots (QDs) within amine-terminated hyperbranched poly(amidoamine)s (HPAMAM) was proposed in this paper. CdTe precursors were first prepared by adding NaHTe to aqueous Cd²⁺ chelated by 3-mercaptopropionic sodium (MPA-Na), and then HPAMAM was introduced to stabilize the CdTe precursors. After microwave irradiation, highly fluorescent and stable CdTe QDs stabilized by MPA-Na and HPAMAM were obtained. The CdTe QDs showed a high quantum yield (QY) up to 58%. By preparing CdTe QDs within HPAMAM, the biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs can be combined, endowing the CdTe QDs with biocompatibility. The resulting CdTe QDs can be directly used in biomedical fields, and their potential application in bio-imaging was investigated.     

Facile preparation of cds quantum dots using hyperbranched poly(amidoamine)s with hydrophobic end‐groups as nanoreactors

Hyperbranched poly(amidoamine)s with methyl ester terminals (HPAMAM) were synthesized by one‐pot approach and subsequently used as nanoreactors to prepare CdS quantum dots (QDs). HPAMAM could bind Cd²⁺ through their internal amines, while the external methyl ester groups prevented the aggregation of polymers. After reaction with S^2?, CdS QDs sequestered within individual hyperbranched polymers were obtained. The resulting CdS/HPAMAM nanocomposites were characterized by dynamic light scattering, transmission electron microscopy, ultraviolet‐visible spectroscopy, photoluminescence spectroscopy, and Fourier transform infrared spectroscopy, confirming the formation of CdS QDs with small particle size and narrow size‐distribution. Furthermore, the effects of Cd²⁺/S^2? ratio and aging time on the photoluminescence of CdS QDs were also investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fluorescence studies of quantum dots and zinc tetraamino phthalocyanine conjugates

CdTe Qds capped with mercapto propionic acid (MPA) were covalently linked to zinc tetraamino phthalocyanine (ZnTAPc) using N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) as the coupling agents. The results presented give evidence in favour of the formation of an amide bond between ZnTAPc and CdTe QDs. Both the linked ZnTAPc–QD complexes and a mixture of QDs and ZnTAPc (i.e. without chemical linking) showed Förster resonance energy transfer (FRET). ZnTAPc quenched the QDs emission, giving quenching constants in the order of 10³ M⁻¹.     

A new two‐phase route to cadmium sulfide quantum dots using amphiphilic hyperbranched polymers as unimolecular nanoreactors

A new two‐phase route was developed to prepare monodisperse cadmium sulfide (CdS) quantum dots (QDs) with a narrow size distribution. In a two‐phase system, chloroform and water were used as separate solvents for palmitoyl chloride functionalized hyperbranched polyamidoamine (HPAMAM‐PC) and cadmium acetate/sodium sulfide, respectively. The amphiphilic HPAMAM‐PC, with a hydrophilic dendritic core and hydrophobic arms, formed stable unimolecular micelles in chloroform and was used to encapsulate aqueous Cd²⁺ ions. After the reaction with S²⁻ ions from the aqueous phase, monodisperse and uniform‐sized CdS QDs stabilized by HPAMAM‐PC unimolecular micelles were obtained. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120:991–997, 2011     

Transparent,fluorescent, and mechanical enhanced elastomeric composites formed with poly (styrene‐butadiene‐styrene) and SiO2‐hybridized CdTe quantum dots

Transparent poly(styrene‐butadiene‐styrene) (SBS)‐quantum dots (QDs) composites (SBS/CdTe QDs) that simultaneously possess strong photoluminescence (PL) and enhanced mechanical properties are presented for the first time based on the facile blending of SiO₂‐hybridized CdTe QDs with SBS. UV–vis spectrum and fluorescence measurement show that SBS/CdTe QDs composites exhibit good optical properties. The results of transmission electron microscopy show good dispersion of CdTe QDs in the SBS matrix. The results of dynamic mechanical thermal analysis indicate that the micro‐phase separated structure of the SBS is exist in the composites, and the presence of CdTe QDs can lead to an decrease of glass transition temperatures of polybutadiene (PB) and polystyrene(PS) domains. In addition, mechanical tests reveal that the addition of CdTe QDs is a useful approach to improve the mechanical properties of SBS. Meanwhile, the fluorescent photographs taken under ultraviolet light prove that SBS/CdTe QDs composites possess strong PL. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Fabrication of fluorescent poly(l‐lactide‐co‐caprolactone) fibers with quantum‐dot incorporation from emulsion electrospinning for chloramphenicol detection

The on‐site rapid detection of antibiotic residues deposited in food or beverage still remains a challenge in daily life. In this study, cadmium tellurium (CdTe) quantum dots (QDs) were incorporated into poly(l ‐lactide‐co‐caprolactone) (PLLACL) fibers with emulsion electrospinning. Water‐soluble CdTe QDs were used as fluorescence agents, and PLLACL was used as filament materials, respectively. A variety of experiments were performed to characterize the structure and properties of the fibrous composite. Ultraviolet–visible and photoluminescence spectra of the fibers showed similar characteristic absorption and emission properties to those of the CdTe QDs. The fibrous QD–PLLACL composite showed stable fluorescence over 30 days at room temperature and could be used to detect chloramphenicol through fluorescence quenching caused by resonance energy transfer. This approach provides a facile shortcut for fabricating fluorescent fibers that simultaneously inherit the mechanical behavior of PLLACL fibers and the fluorescence properties of CdTe QDs for the detection of antibiotics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44584.     

Luminescent properties of CdTe quantum dots synthesized using 3-mercaptopropionic acid reduction of tellurium dioxide directly

A facile one-step synthesis of CdTe quantum dots (QDs) in aqueous solution by atmospheric microwave reactor has been developed using 3-mercaptopropionic acid reduction of TeO₂ directly. The obtained CdTe QDs were characterized by ultraviolet–visible spectroscopy, fluorescent spectroscopy, X-ray powder diffraction, multifunctional imaging electron spectrometer (XPS), and high-resolution transmission electron microscopy. Green- to red-emitting CdTe QDs with a maximum photoluminescence quantum yield of 56.68% were obtained.     

Enhanced photoluminescence quantum yield of red-emitting CdTe:Gd3+ QDs for WLEDs applications

In order to improve the quantum yield of red-emitting CdTe quantum dots (QDs), CdTe:Gd³⁺ QDs were synthesized by a facile one-step aqueous method. The composition, morphology, and photoluminescence property of CdTe:Gd³⁺ QDs were characterized. The results show that the doping of Gd³⁺ not only leads to a red-shift in the emission wavelength but also improves the photoluminescence quantum yield (PL QY) of CdTe QDs up to 85.74%. Doping of Gd element causes the Te dangling bond on the surface of CdTe QDs to be destroyed, thus reducing the nonradiative surface recombination, which is considered to be the reason of the increase in PL QY of CdTe QDs. Finally, high color rendition white light was generated from the CdTe:Gd³⁺ QDs-assisted phosphor-converted white light-emitting diode (WLED). Under operation of 50 mA forward bias current, the fabricated WLED emitted bright warm white light with a high color rendering index of 86, a low correlated color temperature (CCT) of 4020 K, a suitable Commission Internationale de l’Eclairage color coordinates of (0.3651, 0.3223), and an enhanced luminous efficiency of 68.52 lm/W.     

Microfluidic assembly of uniform fluorescent microbeads from quantum‐dot‐loaded fluorine‐containing microemulsion

We report a facile strategy for fabricating fluorescent quantum dot (QD)‐loaded microbeads by means of microfluidic technology. First, a functional fluorine‐containing microemulsion was synthesized with poly[(2‐(N‐ethylperfluorobutanesulfonamido)ethyl acrylate)‐co‐(methyl methacrylate)‐co‐(butyl acrylate)] (poly(FBMA‐co‐MMA‐co‐BA)) as the core and glycidyl methacrylate (GMA) as the shell via differential microemulsion polymerization. Then, CdTe QDs capped with N‐acetyl‐l ‐cysteine (NAC) were assembled into the poly(FBMA‐co‐MMA‐co‐BA‐co‐GMA) microemulsion particles through the reaction of the epoxy group on the shell of the microemulsion and the carboxyl group of the NAC ligand capped on the QDs. Finally, fluorescent microbeads were fabricated using the CdTe QD‐loaded fluorine‐containing microemulsion as the discontinuous phase and methylsilicone oil as the continuous phase by means of a simple microfluidic device. By changing flow rate of methylsilicone oil and hybrid microemulsion system, fluorescent microbeads with adjustable sizes ranging from 290 to 420 µm were achieved. The morphology and fluorescent properties of the microbeads were thoroughly investigated using optical microscopy and fluorescence microscopy. Results showed that the fluorescent microbeads exhibited uniform size distribution and excellent fluorescence performance. © 2014 Society of Chemical Industry     

Alternative procedure for the incorporation of quantum dots into poly(N‐isopropyl acrylamide‐co‐acrylic acid) microgels based on multiple interactions

Monodisperse fluorescent poly(N‐isopropyl acrylamide‐co‐acrylic acid) microgels doped with quantum dots (QDs) were fabricated as follows. First, cysteamine‐capped cadmium telluride (CA–CdTe) QDs were introduced into the microgels at pH 7 by electrostatic interactions. Afterward, the CA–CdTe QDs were further immobilized in the microgels by the collapse of the polymer network when the pH of solution was adjusted to 4. In this system, there existed multiple interactions between the CA–CdTe QDs and the microgels, including hydrogen bonds, electrostatic interactions, and coordination bonds. The photoluminescence intensity and maximum emission wavelength of the resulting microgels could be easily adjusted by changes in the content of the CA–CdTe QDs in the hybrid microgels (HMs) and with differently sized QDs, respectively. We found that the lower the addition of CA–CdTe QDs was, the bigger the blueshift of the photoluminescence spectra of the HMs was and the weaker the photoluminescence intensity was. Finally, temperature‐responsive emission of the HMs was examined. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43227.     

Liver Toxicity of Cadmium Telluride Quantum Dots (CdTe QDs) Due to Oxidative Stress in Vitro and in Vivo

With the applications of quantum dots (QDs) expanding, many studies have described the potential adverse effects of QDs, yet little attention has been paid to potential toxicity of QDs in the liver. The aim of this study was to investigate the effects of cadmium telluride (CdTe) QDs in mice and murine hepatoma cells alpha mouse liver 12 (AML 12). CdTe QDs administration significantly increased the level of lipid peroxides marker malondialdehyde (MDA) in the livers of treated mice. Furthermore, CdTe QDs caused cytotoxicity in AML 12 cells in a dose- and time-dependent manner, which was likely mediated through the generation of reactive oxygen species (ROS) and the induction of apoptosis. An increase in ROS generation with a concomitant increase in the gene expression of the tumor suppressor gene p53, the pro-apoptotic gene Bcl-2 and a decrease in the anti-apoptosis gene Bax, suggested that a mitochondria mediated pathway was involved in CdTe QDs’ induced apoptosis. Finally, we showed that NF-E2-related factor 2 (Nrf2) deficiency blocked induced oxidative stress to protect cells from injury induced by CdTe QDs. These findings provide insights into the regulatory mechanisms involved in the activation of Nrf2 signaling that confers protection against CdTe QDs-induced apoptosis in hepatocytes.     

Flexible fluorescent films based on quantum dots (QDs) and natural rubber

This article presents the fabrication and characterization of polyisoprene fluorescent films doped with CdTe quantum dots (QDs). The biopolymer (polyisoprene) is extracted from natural rubber latex, generating flexible and transparent films in visible range (transmittance over 90%) ideal as a matrix to support QDs. The water solubility of the biopolymer facilitates its doping with water dispersed QDs at room temperature to obtain the fluorescent films. Thermogravimetric analysis reveals that QDs have no significant effect on the thermal properties of the biopolymer. Photophysical characterization of the solution and solid state (films) of the QDs evidenced that the polymer matrix does not influence its emission properties, the maximum fluorescence peaks have only 2 nm of difference between the solution and solid state (films) samples. Therefore, polyisoprene from natural rubber can be considered as an excellent flexible matrix to fabricate fluorescent films with QDs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45459.     

Rapid green manufacture of high yield CdTe@Ca(OH)2 nanocrystals and their performance on WLED

The bottleneck of large‐scale production of semiconductor quantum dots (QDs) is how to solve heavy metal ions waste water and the rapid separation during industrial process. A facile strategy for fabricating CdTe@Ca(OH)₂ nanocrystals exhibiting both improved photoluminescence (PL) stability and prolonged PL lifetime via an economical coprecipitating technology is reported herein. The procedure on capping CdTe QDs into Ca(OH)₂ crystals can enable the products to be easily filtrating separation and the content of residual Cd²⁺ filtrate solution to be reached to 0.238 ppm level. Also, fluorescent rod‐like heterocrystals by addition of saturated CaCl₂ solution is constructed. CdTe@Ca(OH)₂ nanocrystals is utilized further as phosphor powders to construct white light emitting diode (WLED). The WLED presented, here, has good photoelectric properties with color rendering index of 82.4 at 350 mA, a color temperature of 4643 k, and Commission Internationale de L'Eclairage coordinate of (0.3548, 0.3532), belonging to the white gamut, showing great potential in industrial application. © 2015 American Institute of Chemical Engineers AIChE J, 62: 580–588, 2016     

水溶性CdTe量子点的制备和表面修饰及表征

近年来,半导体纳米晶CdTe引起人们越来越多的关注。它具有吸收光谱宽,发射光谱窄而对称,发光颜色可调,荧光强度和光稳定性高等特点,已经广泛用于生物标记,生物传感及生物检测领域。尤其在基于荧光共振能量转移原理的生物传感领域,量子点有望取代有机荧光发色基团作为能量供体。在文章实验中,以巯基丙酸(MPA)作为稳定剂,在水相中合成了CdTe量子点,并考察了回流时间,反应温度,溶液pH对CdTe光学性质的影响。利用透射电子显微镜(TEM),荧光分光光度计(FS)等手段对产物进行分析和表征。结果表明:在pH为9.1,反应温度为30℃,回流5 h,可以实现CdTe的优化合成。在紫外灯(254 nm)照射下,回流时间从1 h到7 h所得到的CdTe量子点,颜色由绿色变到黄色,对应的荧光光谱图的吸收峰位从515 nm(回流1 h)红移到573 nm(回流7 h),证实了CdTe量子点的尺寸随着回流时间的增长而增加。由TEM结果,所合成的CdTe量子点分散性好,且粒径大约在5 nm左右。该本实验制备的CdTe量子点具有较高的荧光强度和量子效率,将在生物标记,生物传感,生物成像等领域有重要作用。     

含CdTe量子点的荧光聚合物和含芘丁酸的荧光聚合物的合成、表征及荧光共振能量转移

报道了一种室温下制备CdTe量子点-聚合物纳米荧光聚合物的方法。首先,使用巯基乙酸(TGA)作为稳定剂在水相中合成CdTe量子点,通过十六三甲基溴化铵(CTAB)将其转移进有机相中。使用N,N-二环己基碳二亚胺(DCC)作为脱水剂将量子点挂接到侧链含有羟基的聚丙烯酸酯(CPA)上。该荧光聚合物CdTe-CPA在室温下合成,能够促进碲化镉量子点-聚合物复合物的荧光性能和稳定性。我们还通过相同的方法,将1-芘丁酸(PBA)连接到聚丙烯酸酯侧链上合成了另一种荧光聚合物P-CPA。对产物通过傅里叶变换红外光谱(FI-IR)、凝胶渗透色谱(GPC)、差示扫描量热(DSC)、透射电镜(TEM)及荧光光谱进行表征。此外还研究了P-CPA和CdTe-CPA间的荧光共振能量转移(FRET)。从吸收和荧光发射光谱得到的数据表明,在二氯甲烷溶液中,从P-CPA到CdTe-CPA间发生了荧光共振能量转移。     

Fluorescent polymer with CdTe quantum dots and 1,8‐naphthahmide fluorescent polymer: Synthesis,characterization, and FRET

In this paper, we reported a new method to fabricate CdTe quantum dots (CdTe QDs), which were synthesized in aqueous solution using thioglycolic acid and L ‐phenylalanine (L ‐Phe) as costabilizing agent. Then, they were transferred into organic phase with the assistance of cetyltrimethylammonium bromide (CTAB) for further utilization. Finally, we use toluene diisocyanate as a bridge between CdTe QDs and polyacrylate (CPA), whose side chain has hydroxyl group, to synthesize a fluorescent composite polymer CdTe‐CPA. In addition, we synthesized an organic substance 4‐[2,4‐di(tert‐butyl)]phenoxy‐N‐(2‐hydroxyethyl)‐1,8‐naphthalimide (N), and obtained 1,8‐naphthahmide fluorescent polymer N‐CPA in the same way as it did on CdTe‐CPA. The resulting materials were characterized by Fourier transform infrared spectroscopy (FT‐IR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), transmission electron microscope (TEM), and photoluminescence (PL). Then, we studied the fluorescence resonance energy transfer (FRET) between CdTe‐CPA and N‐CPA. The data obtained from absorption and fluorescence emission spectral indicated that the FRET from N‐CPA to CdTe‐CPA could be efficiently triggered in the solution of chloroform. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Anodic electrogenerated chemiluminescence of quantum dots: size and stabilizer matter

The electrogenerated chemiluminescence (ECL) of semiconductor quantum dots (QDs) is generally believed to be independent of particle sizes or the capping agents used. Herein, we demonstrate that CdTe QDs with different sizes and stabilizers evidently exhibit different ECL behavior in aqueous solution. The ECL of CdTe QDs stabilized by 3-mercaptopropionic acid (MPA) displays two waves at potentials of about +1.17 V and +1.74 V vs. Ag/AgCl, respectively. ECL spectra confirm that the ECL of QDs is attributed to their band gap luminescence, in which the peak positions are changed with QD sizes. The ECL mechanism of CdTe QDs involves superoxide radical generation by reduction of dissolved oxygen at lower potential or water splitting at higher potential. Direct evidence for superoxide radicals in this medium was obtained via electron spin resonance (ESR) experiments. In comparison, the 2-mercaptoethylamine (MEA)-capped CdTe QDs did not exhibit any ECL in air-saturated pH 7.4 PBS. Both ESR and X-ray photon spectroscopy (XPS) experiments revealed that amine groups in MEA-capped QDs were responsible for the absence of ECL. The reaction of an amine group with a superoxide radical leads to the quenching of ECL. The ECL quenching of MPA-capped CdTe QDs was further used to detect melamine. Under the optimum conditions, the inhibited ECL was linear with the logarithm of concentration of melamine within the concentration range of 10(-9) to 10(-5) M and the detection limit was found to be 6.74 × 10(-10) M, which was 100-100?000 times lower than that of the most previous methods.     

水性CdTe量子点在肝癌细胞标记中的应用

采用一种简单的合成方法,用空气中稳定性良好的亚碲酸钠为前体,合成了高质量的CdTe量子点,发射范围从520～620 nm可调,最佳实验条件下发光效率达40%以上。用叶酸修饰的CdTe量子点作为荧光探针,成功标记肝癌细胞,实验结果表明,通过叶酸偶联的CdTe量子点,能有效进入肿瘤细胞内部。     

表面修饰CdTe量子点的合成及其光学特性

在水相中合成高发光性能的CdTe量子点,研究以巯基乙酸(TGA)为稳定剂对CdTe表面进行修饰,制备在水中分散性良好的纳米晶,通过对CdTe量子点合成反应条件的摸索,掌握了其合成的反应规律.同时用紫外分光光度计、荧光分光光度计和透射电子显微镜对其进行了表征.结果表明,回流时间、n(Cd2+):n(HTe-)、反应物浓度、TGA用量、反应体系pH值,对纳米晶的光学性质具有显著影响.回流2 h制得的CdTe纳米粒子直径约为5 nm,其发射峰窄且对称,表现出良好稳定的光学性质.     

CdTe/CdS核壳量子点的合成和指纹检测研究

本文用水相合成法分别合成了巯基乙酸和谷胱甘肽修饰的CdTe/CdS量子点,讨论了不同反应时间对量子点大小的影响。发现随着回流时间延长量子点的粒径逐渐变大,其荧光发射及吸收峰位置也发生相应的红移,从而量子点发光颜色呈现递变。鉴于量子点这一优良的发光特性,将其应用于光滑客体表面潜在指纹的显现,结果表明此方法灵敏度高,简便,快速。