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Combined photon-echo, luminescence and Raman spectroscopies of layered ensembles of colloidal quantum dots
摘要： Low-temperature dynamics in layered ensembles of core-double-shell colloidal CdSe/CdS/ZnS quantum dots is studied using different experimental techniques, including photoluminescence and absorption spectroscopy, luminescence microscopy, photon echo, transmission electronic microscopy and Raman scattering. A combination of different techniques clarify the nature and hierarchy of relaxation processes in the quantum dot (QD)-composite under study for a broad range of temperatures and timescales. The parameters of local phonons in QDs was found coincident by luminescence and Raman spectroscopies. Different contributions to optical spectra broadening has been recognized and attributed to certain properties of QDs: quantum size effect, electron-phonon coupling, spectral diffusion and natural excited state lifetime.
关键词： Raman spectroscopy,optical dephasing,photon echo,luminescence spectra,quantum dots (QDs),electronic microscopy,low temperatures
更新于2025-09-23 15:19:57
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Down-Shifting and Anti-Reflection Effect of CsPbBr3 Quantum Dots/Multicrystalline Silicon Hybrid Structures for Enhanced Photovoltaic Properties
摘要： Over the past couple of decades, extensive research has been conducted on silicon (Si) based solar cells, whose power conversion e?ciency (PCE) still has limitations because of a mismatched solar spectrum. Recently, a down-shifting e?ect has provided a new way to improve cell performances by converting ultraviolet (UV) photons to visible light. In this work, caesium lead bromide perovskite quantum dots (CsPbBr3 QDs) are synthesized with a uniform size of 10 nm. Exhibiting strong absorption of near UV light and intense photoluminescence (PL) peak at 515 nm, CsPbBr3 QDs show a potential application of the down-shifting e?ect. CsPbBr3 QDs/multicrystalline silicon (mc-Si) hybrid structured solar cells are fabricated and systematically studied. Compared with mc-Si solar cells, CsPbBr3 QDs/mc-Si solar cells have obvious improvement in external quantum e?ciency (EQE) within the wavelength ranges of both 300 to 500 nm and 700 to 1100 nm, which can be attributed to the down-shifting e?ect and the anti-re?ection property of CsPbBr3 QDs through the formation of CsPbBr3 QDs/mc-Si structures. Furthermore, a detailed discussion of contact resistance and interface defects is provided. As a result, the coated CsPbBr3 QDs are optimized to be two layers and the solar cell exhibits a highest PCE of 14.52%.
关键词： down-shifting e?ect,solar cell,anti-re?ection property,caesium lead bromide perovskite quantum dots (CsPbBr3 QDs),multicrystalline Si (mc-Si)
更新于2025-09-23 15:19:57
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Sandwich magnetically imprinted immunosensor for electrochemiluminescence ultrasensing diethylstilbestrol based on enhanced luminescence of Ru@SiO2 by CdTe@ZnS quantum dots
摘要： A molecularly imprinted magnetic sensor with electroluminescent tags (MIP-ECL sensor) was developed for ultrasensing diethylstilbestrol (DES). A strategy is exploited to enhance ECL emission of the [Ru(bpy)3]2 +-tripropyl amine (TPrA) system by CdTe@ZnS quantum-dots (QDs) through energy transfer. Magnetically molecularly imprinted nanoparticles (MMIPs NPs) based on Fe3O4@SiO2 carriers are artificial, easily reproducible, and could replace easily inactivated first antibodies for capturing more DES molecules. Functionalized bio-conjugates of single antibody-CdTe@ZnS (Ab-CdTe@ZnS) are for the first time loaded on signal labels of Ru(bpy)3 2 +-doped silica nanocomposites (Ru@SiO2) for signal amplification. The final bio-conjugated signal probes are denoted as Ab-DES/CdTe@ZnS-Ru@SiO2. MMIPs beads that have captured antigens are bio-conjugated with antibody-labeled luminescent probes by specific immunoreactive reaction, and then the luminescent immunocomplex generates ECL signal on the magnetic electrode. The logarithm of ECL intensities depend linearly on the logarithm of DES concentrations in the range from 4.8×10? 4 to 36.0 nM with a detection limit of 0.025 pM. This novel assay is much more sensitive than other MIP sensors, and achieves lower cost and more enhanced stability than other immunosensors. The sensor is significantly potential and has been applied to DES detection in actual environment.
关键词： [Ru(bpy)3]2+-doped silica,Probe-mode ECL sensor,Core-shell QDs,Magnetically imprinted nanoparticles,Diethylstilbestrol,Single antibody sandwich-type
更新于2025-09-23 15:19:57
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Surface polarity engineering of ZnO layer for improved photoluminescence of CsPbBr3 quantum dot films
摘要： The surface polarity of nanocrystalline ZnO film, a typical electron transport material in optoelectronics, is chemically modified using self-assembled monolayer (SAM) of phenethyl trichlorosilane (PETS). The surface treatment is proved to generate a hydrophobic surface by removing the hydroxyl groups on the oxide layer, which reduces the emission quenching of the subsequent CsPbBr3 quantum dot film. In addition, the surface polarity was engineered with varying PETS concentration, thereby contribute to an increased photoluminescence quantum yield (PLQY) by up to 50%. Meanwhile, the thermal stability of photoluminescence was enhanced showing a wide-range temperature tolerance up to 140 ℃.
关键词： SAM,Stability,Surface Polarity,PETS,ZnO,CsPbBr3 QDs
更新于2025-09-23 15:19:57
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Facile Synthesis of Noncytotoxic PEGylated Dendrimer Encapsulated Silver Sulfide Quantum Dots for NIR-II Biological Imaging
摘要： Near-Infrared-II (NIR-II, 1000-1700 nm) bioimaging features high penetration depth and high spatio-temporal resolution compared to traditional fluorescence imaging, but the key is to develop stable and biocompatible NIR-II fluorophores suitable for in vivo applications. Silver sulfide quantum dots (Ag2S QDs) have been demonstrated excellent for in vivo NIR-II imaging with unique optical properties and decent biocompatibility, but they often require complex post modifications for in vivo applications. Herein we demonstrate a facile one-pot strategy to synthesize the PEGylated dendrimer-encapsulated Ag2S QDs useful for in vivo NIR-II imaging. Silver ions were first loaded into the core of acylthiourea-functionalized dendrimer (PEG-PATU) through the coordination between silver ions and acylthiourea groups, followed by the addition of sodium sulfide to form Ag2S QDs in situ. The resulting PEG-PATU Ag2S QDs hold excellent NIR-II fluorescence signal, and thus could be executed for high efficiency labelling and tracking of A549 cancer cells mobility in vivo and real time visualization of vast circulatory network of a mouse.
关键词： in vivo imaging,PEGylated dendrimer,one-pot synthesis,Ag2S QDs,NIR-II bioimaging
更新于2025-09-23 15:19:57
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Hybrid fluorescent liquid crystalline composites: directed assembly of quantum dots in liquid crystalline block copolymer matrices
摘要： Hybrid ?uorescent liquid crystalline (LC) composites containing inorganic quantum dots (QDs) are promising materials for many applications in optics, nanophotonics and display technology, combining the superior emission capability of QDs with the externally controllable optical properties of LCs. In this work, we propose the hybrid LC composites that were obtained by embedding CdSe/ZnS QDs into a series of host LC block copolymers of di?erent architectures by means of a two-stage ligand exchange procedure. The ABA/BAB triblock copolymers and AB diblock copolymers with di?erent polymerization degrees are composed of nematogenic phenyl benzoate acrylic monomer units and poly(4-vinylpyridine) blocks, which are capable of binding to the QD surface. Our results clearly show that the spatial distribution of QDs within composite ?lms as well as the formation of QD aggregates can be programed by varying the structure of the host block copolymer. The obtained composites form a nematic LC phase, with isotropization temperatures being close to those of the initial host block copolymers. In addition, the in?uence of the molecular architecture of the host block copolymers on ?uorescence properties of the obtained composites is considered. The described strategy for the QD assembly should provide a robust and conventional route for the design of highly ordered hierarchical hybrid materials for many practical applications.
关键词： liquid crystalline block copolymer matrices,ligand exchange procedure,fluorescence properties,CdSe/ZnS QDs,nematic LC phase,Hybrid ?uorescent liquid crystalline composites,quantum dots
更新于2025-09-23 15:19:57
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Cu2AgInSe4 QDs sensitized electrospun porous TiO2 nanofibers as an efficient photoanode for quantum dot sensitized solar cells
摘要： To obtain an efficient quantum dot sensitized solar cell (QDSC), a less toxic quaternary Cu2AgInSe4 QDs with 4.8 nm in size are synthesized by a simple hot injection method. The crystallite size and tetragonal structure are confirmed by XRD and HR-TEM analysis. Energy-dispersive X-ray spectroscopy analysis reveals that the atomic ratio of Cu: Ag: In: Se in the Cu2AgInSe4 QDs is 1.98:1.0:1.03:3.86. The oxidation state of the elements composed in Cu2AgInSe4 QDs is confirmed by XPS studies. Optical properties are studied from the UV–Vis–NIR absorption spectrum and photoluminescence emission spectrum. The porous TiO2 nanofibers (P-TiO2 NFs) are prepared from the conventional electrospun TiO2 NFs followed by the solvosonication process. The FE-SEM analysis is confirmed the porous texture of the TiO2 NFs. The bandgap of the Cu2AgInSe4 QDs and TiO2 NFs are determined from the Tauc plot and it was found to be 1.93 eV and 3.19 eV, respectively. QDSC is assembled using Cu2S counter electrode, polysulfide redox couple electrolyte and Cu2AgInSe4 QDs sensitized P-TiO2 NFs photoanode. The photoconversion efficiency (PCE) of the assembled QDSC is found to be 4.24%.
关键词： Tauc plot,QDSC,Porous TiO2 Nanofibers,Cu2AgInSe4 QDs,Hot injection method
更新于2025-09-23 15:19:57
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Impedimetric detection of Banana bunchy top virus using CdSe quantum dots for signal amplification
摘要： Banana bunchy top virus is considered to be the most economically destructive pathogens of banana that causes severe economic loss in banana plantations worldwide, including India. In this present study we have developed an improved electrochemical ELISA for detection of Banana bunchy top virus (BBTV). For enhanced and accurate detection we have used cadmium selenide (CdSe) quantum dots (QDs) as signal amplifiers. Experiments in this study were performed using primary antibody raised from recombinant coat protein of BBTV. CdSe QDs could significantly amplify the electrical signals in this assay and make the method appropriate for lab use. The result of electrical conduction showed the difference of impedance between the healthy and diseased sample of the order of ~ 100 Ω. The electrochemical ELISA could detect the virus in plant sap up to dilution of 1:25 as compared to 1:10 of conventional ELISA.
关键词： Faradic impedance spectroscopy,Cadmium selenide quantum dots (CdSe QDs),Banana bunchy top virus
更新于2025-09-23 15:19:57
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Synthesis of Water Soluble CuGaS2/ZnS Quantum Dots for Ultrasensitive Fluorescent Detection of Alkaline Phosphatase Based on Inner Filter Effect
摘要： Developing monitoring technique for alkaline phosphatase (ALP) is crucial due to the important role it plays in living cells. Here, a kind of biocompatible glutathione-modified CuGaS2/ZnS quantum dots (GSH-CGS/ZnS QDs) was used as a fluorescent substance and then fabricated “turn-off” fluorescent biosensor for detection of ALP by help of inner filter effect (IFE). Firstly, we prepared CuGaS2/ZnS (CGS/ZnS) QDs using solvothermal method and explored the efficient ligand (GSH) exchanges strategy for transferring oil-soluble CGS/ZnS QDs to aqueous phase. More importantly, we also explored the potential biological applications of the nanohybrid QDs. The obtained GSH-CGS/ZnS QDs emitted strong yellow fluorescence with the maximum excitation (400 nm) and emission (601 nm). Then, GSH-CGS/ZnS QDs were mixed with p-nitrophenylphosphate (PNPP) and ALP. PNPP could be hydrolyzed to p-nitrophenol (PNP) by help of catalysis of ALP, and the excitation spectrum of the GSH-CGS/ZnS QDs overlapped well with the absorption spectrum of PNP, so the fluorescence of GSH-CGS/ZnS QDs was initially quenched via the so-called “IFE”. Finally, a novel “turn-off” biosensor for sensitive detection of ALP in the range of 0.05-10 U L -1(R2 = 0.98) with a detection limit of 0.01 U L-1 was successfully obtained. Results indicated that I-III-VI2 nanocrystals have great potential for their promising biomedical application.
关键词： Inner filter effect,Alkaline phosphatase,GSH-CuGaS2/ZnS QDs,Fluorescent detection,Water solubility and biocompatibility
更新于2025-09-23 15:19:57
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Quantum size effect and surface defect passivation in size-controlled CsPbBr3 quantum dots
摘要： Luminescent CsPbBr3 quantum dots (QDs) with adjustable size and bandgap were grown by controlling the synthesis temperature in this paper. As the synthesis temperature increases, the QD size becomes larger and then smaller. The corresponding absorption and steady-state photoluminescence spectrum indicate that the QD band gap becomes smaller and then larger, which is a typical quantum confinement effect. Time-resolved photoluminescence spectrum and femtosecond transient absorption spectrum (fs-TAS) show that the non-radiative recombination probability of photocarriers in small QDs is small it has few defects, indicating that the ligand molecules adsorbed on the surface of QDs effectively passivate the surface defects of CsPbBr3. Finally, the hot-phonon bottleneck effect of CsPbBr3 QDs is revealed by the kinetic curves fitting of fs-TAS and the cooling kinetic process of hot carriers is also discussed in detail. This work provides new insights on size-dependent photophysical properties of CsPbBr3 QDs.
关键词： Quantum confinement effect,Metal halide perovskite QDs,Defect passivation,Hot carriers
更新于2025-09-23 15:19:57