Water-dispersible Quantum Dots Research Articles

Combination of colorimetry, inner filter effect-induced fluorometry and smartphone‑based digital image analysis: A versatile and reliable strategy for multi-mode visualization of food dyes

Herein, a multi-mode visualization platform was initiated for in-situ detection of food dyes (FDs) by combining colorimetry, fluorometry and smartphone‑based digital image analysis, in which water-dispersible quantum dots (QDs) were served as nanoprobes. Colorimetry was achieved by color comparison, while both fluorometry and fluorescence quantification were performed through inner filter effect (IFE)-induced fluorescence quenching, then color information (RGB & gray-scale values) of colorimetry and fluorometry was picked by a smartphone to reconstruct digitized alignments. Since IFE mechanism was concentration-dependent but did not rely on the interaction between fluorophore and quencher, the whole process of fluorescence response could be finished within 10 s, and both color gradients and fluorescence changes showed fine mappings to FDs concentrations in the range of 1.0 × 10−3∼0.035 mg/mL for brilliant blue, and 1.0 × 10−4∼0.1 mg/mL for Allura red and sunset yellow. As a proof-of-concept, the in-situ multi-mode visualization of these FDs in real beverages was experimentally proved to be highly feasible and reliable as compared with instrumental techniques like UV–vis/fluorescence spectrometry, along with HPLC. Finally, this strategy was extended to the multi-mode visualization of non-food dyes in three simulated wastewater samples with high credibility by contrast with the true additive amounts of model dyes.

Investigation of Ag doping and ligand engineering on green synthesized CdS quantum dots for tuning their optical properties

We present a green route for the colloidal synthesis of undoped and silver (Ag) doped cadmium sulfide (CdS) quantum dots (QDs). We have used olive oil as the reaction medium, which acted as a source of oleic acid (OA) ligand in the green synthesis of CdS QDs. With the increase in OA concentration, the dispersibility of CdS QDs improved. The water-dispersible CdS QDs were prepared via exchanging OA’s associated ligand with 3-mercaptopropionic acid (MPA). The MPA-capped CdS QDs showed the disappearance of the S-H peak as characterized via FTIR. The crystal and optical properties of Ag-doped CdS QDs were investigated, and the spectral red shift in the absorption spectra was observed. The CdS QDs with low Ag doping concentration increased the lifetime of excitons, but the average lifetime was suppressed at a higher concentration. We also discussed the variation in the properties of the CdS QDs through ligand engineering and Ag doping. These doped and undoped QDs have the potential for applications in photocatalysis, water splitting, solar cells, etc. In addition, water dispersible QDs can be helpful for bioimaging, and drug delivery applications

Application of Water-Dispersed Quantum Dots to Crack Monitoring in Smart Composite Materials

Heterostructurally engineered CdZnSeS@ZnS quantum dots (QD) materials are synthesized through surface modification involving ligand exchange, changing the surface chemistry from hydrophobicity to hydrophility. The hydrophilic characteristics of the CdZnSeS@ZnS QDs are exploited in the artificial monitoring of the cracks present in the smart composite building materials. The synthesized CdZnSeS@ZnS QDs demonstrate that the average sizes of CdZnSeS and CdZnSeS@ZnS QDs are 9.5 and 12.7 nm, respectively. The presence of ZnS shell (~1.6 nm) functions as an effective physical barrier in order to enhance the stability of QDs against environmental changes such as the ligand exchange process. The optimized CdZnSeS@ZnS QDs, exhibit high-quality fluorescent features with a peak emission wavelength of 525 nm. The current work chose the shape memory alloy(SMA)/cement composites as a model system of cement-based materials, due to its applicability to self-healing functions mediated through shape memory alloys immersed into the cementitious matrix. The SMA/cement composites are subjected to the hostile mechanical loading, leading to mechanical defects, cracks and subsequently were heated to heal cracks mechanically generated. The insertion of aqueous QD solutions to the recovered SMA/cement composites is evaluated in terms of structural health monitoring. Unlike the previous crack monitoring approaches, the water-dispersed QD materials demonstrate the facilitated infiltration to the crack networks and the effective monitoring capability with the aid of highly luminescent quantum dots. The unique features are discussed with the main emphasis on the hydrophilic properties of the CdZnSeS@ZnS QDs. The aqueous QD solution approach is proven to be suitable for monitoring complex cracks and self-healing features in smart composite materials which will be employed in buildings and infrastructures.

Ecotoxicology impact of silica-coated CdSe/ZnS quantum dots internalized in Chlamydomonas reinhardtii algal cells

The use of quantum dots (QD) in various medical and industrial applications may cause these nanoparticles to leak into waterways and subsequently enter the food chain. Therefore, if we intend to use QD, we must first know their potential environmental implications. In this work, cadmium selenide/zinc sulfide core/shell QD were synthesized, and then, biocompatible, water-dispersed QD were coated with silica (Si-QD). The QD were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) combined with energy-dispersive X-ray spectroscopy (EDX), and UV–Vis absorption analysis, which revealed that these surface-engineered QD have a highly crystalline, homogeneous spherical shape measuring approximately 25 nm. The cytotoxicity of the nanoparticles in the green algae Chlamydomonas reinhardtii was studied by incubating the algae cells with Si-QD and determining the optical density of algal cell culture, cell counts, and cells sizes by microflow cytometry. These measurements indicated that Si-QD are biocompatible up to a concentration of 25 ng/ml. Finally, the cellular uptake of Si-QD into C. reinhardtii was monitored by confocal laser scanning microscopy (CLSM). In conclusion, our results reveal that surface-engineered Cd-QD can penetrate the cells of aquatic organisms, which ensures a serious impact on the food chain and consequently the environment. On the other hand, the results also highlight a new potential method for bioremediation of Cd-QD by green algae, especially C. reinhardtii.

Crack monitoring in shape memory alloy/cement composite materials using water-dispersed quantum dots

Highly luminescent, heterostructurally engineered CdZnSeS@ZnS quantum dot (QD) materials are surface-modified through ligand exchange from hydrophobicity to hydrophilicity, by which the QD surface becomes compatible with the cementitious materials fabricated from a water-based constituent. Facile structural health monitoring tools are proposed based on aqueous QD material applied to mechanical defects encountered in cement-based materials and similar massive infrastructure. Unlike the pre-existing materials approach, the current work employed water as the dispersion medium, which is compatible with the pre-existing structural environment, thus facilitating infiltration of the aqueous solution into the porous or cracked cement-based systems. The aqueous QD solutions are proven to be suitable for crack monitoring in cement-based materials.

All Aqueous Synthesis of Silica Encapsulated Quantum Dots with Functional Shells

All-aqueous synthesis of silica-encapsulated quantum dots with functional shells Huanhuan Feng[abc], Jan Bart ten Hove[d], Tingting Zheng[ae], Aldrik H. Velders[d] and Joris Sprakel∗[a] We present a simple yet versatile method for encapsulating water-dispersed quantum dots (QDs) in a silica shell. As our approach, does not require ligand exchange, the colloidal stability of the quantum dots is maintained throughout the process, which results in monodisperse core-shell particles of individual quantum dots with a well-defined silica shell whose thickness can be accurately controlled. While other methods often result in a reduction of luminescence, our approach can retain all or even increases the quantum efficiency of the semiconductor dots. We also show how amine-functional groups can be expressed at the surface of the silica shell, while retaining QD photoluminescence properties, allowing further surface functionalization. Finally, we demonstrate the versatility of this strategy by including dopants into the silica shells to tailor the spectral response of the core-shell particles by energy transfer. [a] Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, the Netherlands [b] Dutch Polymer Institute (DPI), P.O. Box 902, 5200 AX Eindhoven, the Netherlands [c] School of Materials Science and Engineering, Harbin Institute of Technology (Shenzhen), China [d] Laboratory of BioNanoTechnology, Wageningen University & Research, Bornse Weilanden 9,6708 WG Wageningen, The Netherlands [e] Shenzhen Key Laboratory for Drug Addiction and Medication Saftey, Department of Ultrasound, Peking University Shenzhen Hospital & Biomedical Research Institute, Shenzhen-PKU-HKUST Medical Center, Shenzhen 518036, China.

All‐Aqueous Synthesis of Silica‐Encapsulated Quantum Dots with Functional Shells

We present a simple yet versatile method for encapsulating water‐dispersed quantum dots (QDs) in a silica shell. As our approach, does not require ligand exchange, the colloidal stability of the quantum dots is maintained throughout the process, which results in monodisperse core‐shell particles of individual quantum dots with a well‐defined silica shell whose thickness can be accurately controlled. While other methods often result in a reduction of luminescence, our approach can retain all or even increases the quantum efficiency of the semiconductor dots. We also show how amine‐functional groups can be expressed at the surface of the silica shell, while retaining QD photoluminescence properties, allowing further surface functionalization. Finally, we demonstrate the versatility of this strategy by including dopants into the silica shells to tailor the spectral response of the core‐shell particles by energy transfer.

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

ABSTRACTThis 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.

Water-Dispersed Quantum Dots of Coordination Polymers with Strong Photoluminescence

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Water-dispersed quantum dots of coordination polymers with strong photoluminescence

Coordination polymers PZn quantum dots with a uniform diameter of 3 ± 0.5 nm were successfully prepared. The PZn QDs exhibit excellent water dispersibility, high photoluminescence, outstanding photostability and remarkable biocompatibility. The results of cellular experiments show that the PZn QDs are highly suitable for long-term cell imaging.