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Passively Q-switched erbium-doped fiber laser using quantum dots CdSe embedded in polymer film as saturable absorber
摘要： We demonstrate a passively Q-switched erbium doped fiber laser (EDFL) based on quantum dots (QD) CdSe as a saturable absorber (SA). The synthesized CdSe powder was embedded into a poly(methyl methacrylate) (PMMA) using emulsion polymerization process. The film is sandwiched between two fiber connector via an adapter to form a fiber-compatible SA device. By integrating the SA device into the EDFL ring cavity, the stable Q-switched operation is achieved at 1559.35 nm as the pump power is varied within 30–118 mW. The laser has a pump threshold of 20.4 mW. The pulse repetition rate shows an increasing trend from 33.2 to 68.45 kHz, whereas the pulse width exhibits a decreasing trend from 10.04 to 4.30 μs as the pump power is increased from 30 to 118 mW. The highest pulse energy of 11.83 nJ is obtained at a pump power of 118 mW. These results indicate that QD CdSe is a promising SA for Q-switching laser operation.
关键词： Q-switching,Quantum dots CdSe,Saturable absorber
更新于2025-11-28 14:23:57
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Graphene quantum dot based charge-reversal nanomaterial for nucleus-targeted drug delivery and efficiency controllable photodynamic therapy
摘要： Graphene quantum dots (GQD), the new zero-dimensional carbon nanomaterial, has been demonstrated as a promising material for biomedical applications due to its good biocompatibility and low toxicity. However, the integration of multiple therapeutic approaches into a nano-sized platform based on the GQD has not been explored yet to our best knowledge. In this report, we regulate the generation of reactive oxygen species (ROS) when using the GQD as a photosensitizer by varying the doping amount of nitrogen atoms to achieve efficiency controllable photodynamic therapy (PDT). On the other hand, charge-reversal (3-Aminopropyl) triethoxysilane (APTES) was employed to conjugate on the surface of GQD for nucleus targeting drug delivery for the first time. The treatment outcome of produced ROS and nucleus-targeting drug delivery was investigated by fluorescence imaging. The results demonstrated that the N-GQD-DOX-APTES in dual roles as a drug carrier and photosensitizer could achieve nucleus-targeting delivery and strong ROS production simultaneously. This approach provides a promising strategy for the development of multifunctional therapy in one nano platform for biomedical applications.
关键词： nucleus-targeted drug delivery,Graphene quantum dots,nitrogen doped graphene quantum dots,charge-reversal,photodynamic therapy
更新于2025-11-21 11:24:58
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Photoluminescence Intensity Enhancement of Single Silicon Quantum Dots on a Metal Membrane with a Spacer
摘要： Silicon quantum dots (Si QDs) featuring high photoluminescence (PL) intensity are necessary for the realization of different photonic and photovoltaic devices, such as light-emitting diodes (LEDs) and luminescent solar concentrators (LSCs). Herein, Si QDs on a (cid:1)100–200 nm thin silicon dioxide membrane with a metal back-coating are prepared. The dots are formed from the device layer of a silicon-on-insulator (SOI) wafer by etching and thermal oxidation. Aluminum is sputtered on the backside of the membrane, acting as a back-surface mirror, changing the local density of optical modes, as well as the local excitation ?eld. The PL properties of such Si QDs are then characterized at the single-particle level. It is found that the PL yield of single Si QDs on the membrane is enhanced by approximately one order of magnitude, compared with that of Si QDs outside the membrane under the same excitation power. These results indicate that advances in nanofabrication can substantially improve the optical properties of Si QDs, thus paving the way for their application.
关键词： membranes,quantum dots,silicon,blinking,photoluminescence
更新于2025-11-21 11:24:58
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Polymer spacer tunable Purcell-enhanced spontaneous emission in perovskite quantum dots coupled to plasmonic nanowire networks
摘要： Polymer spacer tunable Purcell-enhanced spontaneous emission in perovskite quantum dots coupled to plasmonic nanowire networks? Lead halide perovskite quantum dots (PQDs) have recently been proposed as a scalable and color-tunable quantum source, but their slow spontaneous emission creates a mismatch with high-speed nanophotonic devices. Here, we demonstrate fast and bright emission in PQD films coupled to silver nanowire networks (NWKs), in which polyvinyl alcohol (PVA) is used as a spacer to regulate the lossy characteristics of the plasmonic cavity. Compared with bare quartz, the PVA substrate shows a considerable enhancement effect on the apparent emission intensity, but a reduction in the emission rate of PQD excitons. The efficient NWK–PQD coupling generates an increase in the emission intensity of a factor of 6.0 (average 3.4) and simultaneously a 2.4-fold (average 1.9) enhancement in the emission rate. However, an opposite PVA spacer thickness dependence for Purcell factor and quantum yield is observed, indicating that the fast and bright emission would be a trade-off between the Purcell-enhanced radiative rate and large metal guidance on plasmonic cavity design for perovskite-based nanophotonic devices.
关键词： plasmonic nanowire networks,spontaneous emission,Polymer spacer,Purcell-enhanced,perovskite quantum dots
更新于2025-11-21 11:24:58
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Cancer Cell Targeting With Functionalized Quantum Dot-Encoded Polyelectrolyte Microcapsules
摘要： Imaging agents and drug carriers are commonly targeted toward cancer cell through functionalization with specific recognition molecules. Quantum dots (QDs) are fluorescent semiconductor nanocrystals whose extraordinary brightness and photostability make them attractive for direct fluorescent labeling of biomolecules or optical encoding of the membranes and cells. Here, we analyse the cytotoxicity of QD-encoded microcapsules, validate an approach to the activation of further functionalization with monoclonal antibody Trastuzumab, a humanized monoclonal antibody targeting the extracellular domain of the human epidermal growth factor receptor 2 (HER2) and already in clinical use for the treatment of HER2 positive breast cancer. In addition, we characterize the cell-specific targeting activity of the resultant bio-conjugate by immunofluorescence assay (IFA) and real-time analysis of interaction of the conjugates with live HER2 overexpressing human breast cancer cells. We demonstrate, that encapsulation of QDs into the polymer shell using the layer-by-layer deposition method yields highly fluorescent polyelectrolyte microcapsules with a homogeneous size distribution and biocompatibility upon in vitro treatment of cancer cells. Carbodiimide surface activation ensures optimal disperse and optical characteristics of the QD-encoded microcapsules before antibody conjugation. The prepared conjugates of the microcapsules with cancer-specific monoclonal antibody targeting HER2 provide sufficiently sensitive and specific antibody-mediated binding of the microcapsules with live cancer cells, which demonstrated their potential as prospective cancer cell–targeting agents.
关键词： cytotoxicity,monoclonal antibody,polyelectrolyte microcapsules,quantum dots,cancer cell targeting
更新于2025-11-21 11:24:58
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Cell Imaging Using Two-Photon Excited CdS Fluorescent Quantum Dots Working within the Biological Window
摘要： In recent years, two-photon excited semiconductor quantum dots (QDs) have been the subject of intense investigation due to their long excitation wavelength which helps to achieve deeper penetration and higher image resolution in optical bioimaging. In this paper, water-soluble CdS QDs were synthesized using a hydrothermal method and applied to human liver hepatocellular carcinoma (HepG2) cells. The first-principles calculation suggested that the S-rich defected structure contributes to a narrower band gap compared to the pristine structure. The resulting fluorescence wavelength was significantly red shifted, which was attributed to the deep defect states emission. The large Stokes shifts (> 200 nm) of the QDs can eliminate the possible cross-talk between the excitation light and the emission light. Two-photon induced red fluorescence emission can avoid overlapping with the autofluorescence emission of biological samples. The uptake and cell viability measurements of the HepG2 cells showed a good biocompatibility and a low toxicity of CdS QDs. Two-photon excited scanning microscopy images revealed that the HepG2 cells incubated with CdS QDs emitted bright red upconversion fluorescence and the fluorescence brightness was 38.2 times of that of the control group. These results support CdS QDs as a good candidate for application in cellular imaging.
关键词： two-photon absorption,CdS quantum dots,deep defect states,HePG2 cells,biological imaging
更新于2025-11-21 11:24:58
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Microwave-assisted oleothermal synthesis of graphene-TiO2 quantum dots for photoelectrochemical oxygen evolution reaction
摘要： In this work, it was reported the production of graphene-TiO2-quantum dots based on an oleothermal redox reaction. Using concepts of nanoemulsification, an oil-water stable nanodroplets were formed. This emulsion was treated at different temperatures in an oil-based medium. This is an advantage to obtain well dispersed hydrophilic nanoparticles, considering that using water as solvent promotes their agglomeration. The cluster of hydrate titanium is formed inside the water dispersed graphene oxide nanodroplet in the oil medium. This aspect assures a close connection between graphene layers and titanium ions, originating dispersed quantum dots of minimum size. Temperature and time of oleothermal reaction influence the degree of functionalization of the graphene layers and thus the photoluminescence characteristics. For the water splitting characterization, a transparent thin film was obtained using the electrophoresis. It was possible to correlate the degree of oxygen functionalization of the graphene layers with the oleothermal conditions and the generated photocurrents.
关键词： Oleothermal,Quantum dots,Photoluminescence,Graphene,Photocurrent
更新于2025-11-21 11:18:25
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From colloidal CdSe quantum dots to microscale optically anisotropic supercrystals through bottom-up self-assembly
摘要： The development of fabrication techniques for novel nanostructured materials is one of the key tasks of modern materials science. One pathway to successfully complete this task is the bottom-up assembly of colloidal nanoparticles into ordered superstructures, possessing both the properties of individual nanoparticles and further novel properties resulting from their interactions. However, nanoparticle self-assembly depends on a variety of parameters, which makes the precise control of this process a complicated problem. Here, the time course of quantum dot (QD) self-assembly into ordered superstructures has been analyzed, along with the evolution of their morphological and optical properties. QD self-assembly occurs through two distinct stages (homo- and hetero-geneous), leading to the formation of supercrystals with a layered morphology. Analysis of the optical properties throughout the superstructures’ growth has shown that the absorption and photoluminescence (PL) bands are blue shifted, retaining almost the same PL lifetimes as in the initial QD solution. The supercrystals formed possess a further unique optical property caused by their layered morphology; namely, a four-fold symmetry characterized by strong birefringence. Such supercrystals may be used for the fabrication of microscale optical paths with high extinction coefficients and specific polarization properties for novel optoelectronic devices.
关键词： optical anisotropy,nanostructured materials,birefringence,self-assembly,quantum dots,supercrystals
更新于2025-11-21 11:08:12
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Hydrophilic Quantum Dots Functionalized with Gd(III)-DO3A Monoamide Chelates as Bright and Effective T1-weighted Bimodal Nanoprobes
摘要： Magnetic resonance imaging (MRI) is a powerful non-invasive diagnostic tool that enables distinguishing healthy from pathological tissues, with high anatomical detail. Nevertheless, MRI is quite limited in the investigation of molecular/cellular biochemical events, which can be reached by fluorescence-based techniques. Thus, we developed bimodal nanosystems consisting in hydrophilic quantum dots (QDs) directly conjugated to Gd(III)-DO3A monoamide chelates, a Gd(III)-DOTA derivative, allowing for the combination of the advantages of both MRI and fluorescence-based tools. These nanoparticulate systems can also improve MRI contrast, by increasing the local concentration of paramagnetic chelates. transmetallation assays, optical characterization, and relaxometric analyses, showed that the developed bimodal nanoprobes have great chemical stability, bright fluorescence, and high relaxivities. Moreover, fluorescence correlation spectroscopy (FCS) analysis allowed us to distinguish nanosystems containing different amounts of chelates/QD. Also, inductively coupled plasma optical emission spectrometry (ICP – OES) indicated a conjugation yield higher than 75%. Our nanosystems showed effective longitudinal relaxivities per QD and per paramagnetic ion, at least 5 times [per Gd(III)] and 100 times (per QD) higher than the r1 for Gd(III)-DOTA chelates, suitable for T1-weighted imaging. Additionally, the bimodal nanoparticles presented negligible cytotoxicity, and efficiently labeled HeLa cells as shown by fluorescence. Thus, the developed nanosystems show potential as strategic probes for fluorescence analyses and MRI, being useful for investigating a variety of biological processes.
关键词： Quantum Dots,Gd(III)-DO3A monoamide chelates,Fluorescence,MRI,Bimodal nanoprobes
更新于2025-11-21 11:08:12
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Green Preparation of Fluorescent Carbon Quantum Dots from Cyanobacteria for Biological Imaging
摘要： Biomass-based carbon quantum dots (CQDs) have become a significant carbon materials by their virtues of being cost-effective, easy to fabricate and low in environmental impact. However, there are few reports regarding using cyanobacteria as a carbon source for the synthesis of fluorescent CQDs. In this study, the low-cost biomass of cyanobacteria was used as the sole carbon source to synthesize water-soluble CQDs by a simple hydrothermal method. The synthesized CQDs were mono-dispersed with an average diameter of 2.48 nm and exhibited excitation-dependent emission performance with a quantum yield of 9.24%. Furthermore, the cyanobacteria-derived CQDs had almost no photobleaching under long-time UV irradiation, and exhibited high photostability in the solutions with a wide range of pH and salinity. Since no chemical reagent was involved in the synthesis of CQDs, the as-prepared CQDs were confirmed to have low cytotoxicity for PC12 cells even at a high concentration. Additionally, the CQDs could be efficiently taken up by cells to illuminate the whole cell and create a clear distinction between cytoplasm and nucleus. The combined advantages of green synthesis, cost-effectiveness and low cytotoxicity make synthesized CQDs a significant carbon source and broaden the application of cyanobacteria and provide an economical route to fabricate CQDs on a large scale.
关键词： bioimaging,cyanobacteria,carbon quantum dots,hydrothermal method
更新于2025-11-21 11:08:12