Concentration Of Quantum Dots Research Articles

Mercaptopropionic acid-capped CdZnTe Quantum dots as Fluorescence Probe for Sensitive Detection of Cr(III) ions.

Although Cr(III) ions are essential for the human body, excessive amounts can lead to skin inflammation, allergic reactions, and genotoxicity. A highly sensitive fluorescence probe was developed using mercaptopropionic acid (MPA) capped CdZnTe quantum dots (QDs) synthesized via an aqueous solution heating method for precise detection of Cr(III) ions. The synthesized MPA-CdZnTe QDs had a size of 2.38 ± 0.13nm and exhibited a zinc-blende structure, with MPA molecules effectively capping the surface through Cd-S bonds. Investigation into the effects of reflux times and solution pH on the absorption and fluorescence spectra of MPA-CdZnTe QDs revealed the occurrence of Ostwald ripening during prolonged reflux processes. The quantum yield (QY) of the synthesized CdZnTe QDs could reach 89%, and the QY was higher under acidic conditions than alkaline. Leveraging the quenching effect of Cr(III) ions on MPA-CdZnTe QDs, a robust method for the quantitative detection of trace amounts of Cr(III) ions was established. Linear quenching behavior was observed within the concentration range of 3.33 × 10- 6 to 5.00 × 10- 4 mol L- 1 for Cr(III) ions, with the fluorescence quenching rate described by a linear regression equation: 1-F/F0 = 0.218 + 829.5268CCr(III). The limit of detection was determined to be 2.63 × 10- 6 mol L- 1. The mechanism of the fluorescence behavior of MPA capped CdZnTe QDs towards Cr(III) ions was photo-induced electron transfer.

Förster Resonance Energy Transfer and Enhanced Emission in Cs4PbBr6 Nanocrystals Encapsulated in Silicon Nano-Sheets for Perovskite Light Emitting Diode Applications.

Encapsulating Cs4PbBr6 quantum dots in silicon nano-sheets not only stabilizes the halide perovskite, but also takes advantage of the nano-sheet for a compatible integration with the traditional silicon semiconductor. Here, we report the preparation of un-passivated Cs4PbBr6 ellipsoidal nanocrystals and pseudo-spherical quantum dots in silicon nano-sheets and their enhanced photoluminescence (PL). For a sample with low concentrations of quantum dots in silicon nano-sheets, the emission from Cs4PbBr6 pseudo-spherical quantum dots is quenched and is dominated with Pb2+ ion/silicene emission, which is very stable during the whole measurement period. For a high concentration of Cs4PbBr6 ellipsoidal nanocrystals in silicon nano-sheets, we have observed Förster resonance energy transfer with up to 87% efficiency through the oscillation of two PL peaks when UV excitation switches between on and off, using recorded video and PL lifetime measurements. In an area of a non-uniform sample containing both ellipsoidal nanocrystals and pseudo-spherical quantum dots, where Pb2+ ion/silicene emissions, broadband emissions from quantum dots, and bandgap edge emissions (515 nm) appear, the 515 nm peak intensity increases five times over 30 min of UV excitation, probably due to a photon recycling effect. This irradiated sample has been stable for one year of ambient storage. Cs4PbBr6 quantum dots encapsulated in silicon nano-sheets can lead to applications of halide perovskite light emitting diodes (PeLEDs) and integration with traditional semiconductor materials.

Synthesis and Characterization of Cu<sub>2</sub>O/ CuO Quantum Dots as Photocatalyst for Lignin Depolymerization via Reactive Oxygen Species: A Preliminary Study

Lignin is a type of polymer with diverse functional groups that can be transformed into biofuels and various high-value chemicals. By utilizing light energy and operating at low temperatures, photocatalysis via Reactive Oxygen Species (ROS) becomes a promising strategy to develop further. However, the revelation of photocatalyst mechanisms in ROS production to improve the efficiency and effectiveness of lignin transformation is still limited. This study aims to determine the effect of Cu2O/CuO quantum dots (QDs) concentration in the photocatalyst system on lignin depolymerization via ROS. The wet chemical method was used to synthesize Cu2O/CuO QDs. The property determination of absorbance, crystallinity, and particle morphology is characterized using uv-vis, X-ray diffraction (XRD), and Transmission Electron Microscope (TEM) instrument. The ROS production was measured using a UV-vis instrument by varying the Cu2O/CuO QDs concentration (1, 3, and 5 μM). The depolymerization sign was observed using a Fourier-Transform Infrared Spectroscopy (FTIR) instrument. The result shows that the synthesized material has a Cu2O/CuO phase with an average particle size of 8 nm and a band gap value of 2.35 eV. The optimum ROS production activity was achieved at the Cu2O/CuO QDs 3 μM concentration, reaching ten mM/sec. The FTIR result also confirms that the functional group transformation occurred. Overall, this study provides brief insight for further optimization of the lignin depolymerization photocatalysis process.

Direct Laser Writing of Micro-Nano Filters Based on Three-Photon Polymerization.

Direct laser writing (DLW) enables the manufacturing of functional quantum dot (QD)-polymer nanostructures with the special performance desired for technological applications. However, most papers fabricate the QD-polymer photoresist based on the principle of two-photon polymerization using laser wavelengths of 750-800 nm, which cannot effectively fabricate the near-infrared QD-polymer photoresist with absorption wavelengths above 800 nm due to linear absorption. Moreover, most papers report a relatively low doping concentration of QDs. To address these issues, this study introduces three-photon DLW technology using a near-infrared 1035 nm laser to effectively avoid the linear absorption of the near-infrared PbS/CdS QD-polymer photoresist. Three kinds of QD-polymer photoresists with concentrations up to 150 mg mL-1 are prepared through surface modification of QDs. We demonstrate that three-photon DLW is feasible to fabricate high-concentration QD-polymer photoresist to produce micro/nano high-performance QD-polymer filters of visible and near-infrared light absorption. This study provides materials and process guidance for the fabrication and application of visible and near-infrared optical filters through three-photon DLW processing of various kinds of functional nanoparticles-polymer photoresist.

Paper-Based Fluorescent Sensor for Rapid Multi-Channel Detection of Tetracycline Based on Graphene Quantum Dots Coated with Molecularly Imprinted Polymer.

In this paper, we developed a paper-based fluorescent sensor using functional composite materials composed of graphene quantum dots (GQDs) coated with molecularly imprinted polymers (MIPs) for the selective detection of tetracycline (TC) in water. GQDs, as eco-friendly fluorophores, were chemically grafted onto the surface of paper fibers. MIPs, serving as the recognition element, were then wrapped around the GQDs via precipitation polymerization using 3-aminopropyltriethoxysilane (APTES) as the functional monomer. Optimal parameters such as quantum dot concentration, grafting time, and elution time were examined to assess the sensor's detection performance. The results revealed that the sensor exhibited a linear response to TC concentrations in the range of 1 to 40 µmol/L, with a limit of detection (LOD) of 0.87 µmol/L. When applied to spiked detection in actual water samples, recoveries ranged from 103.3% to 109.4%. Overall, this paper-based fluorescent sensor (MIPs@GQDs@PAD) shows great potential for portable, multi-channel, and rapid detection of TC in water samples in the future.

Lead sulfide quantum dots in an organic solar cell active layer

Organic solar cells have been fabricated using various concentrations of lead sulfide quantum dots. Data from Mott–Schottky analysis revealed intriguing changes in the bulk heterojunction layer of the solar cells that were directly related to the addition of the quantum dots. Notably, the highest power conversion efficiency of 5.15% was achieved with the addition of 0.4 wt% lead sulfide quantum dots.

Graphene-PbS Quantum Dot Heterostructure for Broadband Photodetector with Enhanced Sensitivity.

Photodetectors converting light into electrical signals are crucial in various applications. The pursuit of high-performance photodetectors with high sensitivity and broad spectral range simultaneously has always been challenging in conventional semiconductor materials. Graphene, with its zero bandgap and high electron mobility, is an attractive candidate, but its low light absorption coefficient restricts its practical application in light detection. Integrating graphene with light-absorbing materials like PbS quantum dots (QDs) can potentially enhance its photodetection capabilities. Here, this work presents a broadband photodetector with enhanced sensitivity based on a graphene-PbS QD heterostructure. The device leverages the high carrier mobility of graphene and the strong light absorption of PbS QDs, achieving a wide detection range from ultraviolet to near-infrared. Employing a simple spinning method, the heterostructure demonstrates ultrahigh responsivity up to the order of 107 A/W and a specific detectivity on the order of 1013 Jones, showcasing significant potential for photoelectric applications.

Preparation and optimization of grafted hydroxyethyl cellulose, polypyrrole, and nitrogen-doped carbon quantum dots bionanocomposites for electrical, optical, and photoluminescence multicoloring applications

The major objective of this research revolves around the integration of polypyrrole (PPy) and various concentrations of nitrogen-doped carbon quantum dots (N-CQDs) into a polyacrylamide (PAm)-grafted hydroxyethyl cellulose (gHEC) to produce gHEC@PPy@N-CQDs bionanocomposites that possess environmentally sustainable properties. The intercalation and uniform distribution of N-CQDs inside the gHEC@PPy matrix have been demonstrated through the analysis of data obtained from X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The samples underwent analysis using thermogravimetric analysis (TGA and DTG) as well as scanning and transmission electron microscopy. The improved dispersion of PPy and 4 % N-CQDs inside the matrix led to enhanced electrical characteristics of the graphene-hybridized metal bionanocomposite. The peculiar optical and photoluminescence emission observed in the gHEC@PPy@N-CQDs bionanocomposites can be attributed to the surface groups of N-CQDs and the transition between CN and CN. This hypothesis suggests that these factors play a significant role in determining the observed optical properties. The main goal is to identify distinctive and captivating applications for these bionanocomposites across several domains, including electronics, optical and light-emitting devices with a broad spectrum of colors, and bioimaging applications.

Visualization of 2D and 3D Tissue Models via Size-Selected Aqueous AgInS/ZnS Quantum Dots.

Three-dimensional (3D) spheroid cell cultures of fibroblast (L929) and tumor mammary mouse (4T1) were chosen as in vitro tissue models for tissue imaging of ternary AgInS/ZnS fraction quantum dots (QDs). We showed that the tissue-mimetic morphology of cell spheroids through well-developed cell-cell and cell-matrix interactions and distinct diffusion/transport characteristics makes it possible to predict the effect of ternary AgInS/ZnS fraction QDs on the vital activity of cells while simultaneously comparing with classical two-dimensional (2D) cell cultures. The AgInS/ZnS fractions, emitting in a wide spectral range from 635 to 535 nm with a mean size from ∼3.1 ± 0.8 to ∼1.8 ± 0.4 nm and a long photoluminescence lifetime, were separated from the initial QD ensemble by using antisolvent-induced precipitation. For ternary AgInS/ZnS fraction QDs, the absence of toxicity at different QD concentrations was demonstrated on 2D and 3D cell structures. QDs show a robust correlation between numerous factors: their sizes in biological fluids over time, penetration capabilities into 2D and 3D cell structures, and selectivity with respect to penetration into cancerous and healthy cell spheroids. A reproducible protocol for the preparation of QDs along with their unique biological properties allows us to consider ternary AgInS/ZnS fraction QDs as attractive fluorescent contrast agents for tissue imaging.

Nonlinear optical absorption and ultrafast carrier dynamics in layered tin diselenide quantum dots

Quantum dots (QDs) derived from typical two-dimensional materials present attractive unique chemical and physical properties because of the quantum-confinement effect. Herein, high-quality layered tin diselenide (SnSe2) QDs with controllable size and thickness were prepared from layered bulk SnSe2 crystals using a simple, effective, and economical mechanical and liquid exfoliation technique. The resulting SnSe2 QDs were subsequently incorporated into chemically stable transparent silica-gel glasses using a sol–gel method. The nonlinear optical (NLO) absorption of the SnSe2 QDs was systematically explored using a combination of open-aperture Z-scan and pump–probe technologies. The derived NLO parameters and ultrafast carrier dynamics of the QDs were comparable to those of reported low-dimensional materials. Interestingly, the layered SnSe2 QDs exhibited thickness/layer-dependent NLO properties and pulse duration-dependent saturable absorption and reverse saturable absorption in both dimethylformamide suspensions and solid silica-gel glasses. Such unique NLO characteristics make layered SnSe2 QDs a promising candidate for technological innovations in areas including optoelectronics and nonlinear optics.

Molecular dynamics simulations on TiO2 quantum dots modified asphalt: Impact of size and concentration of quantum dots

With exceptional solar reflectivity and fluorescent characteristics, TiO2 quantum dots (QDs) modified asphalt has been proposed as an innovative cool pavement technology. However, interaction mechanism and thermodynamic properties of TiO2 QDs modified asphalt at microscale have not been well understood. In this study, electronic and optical properties of TiO2 QDs with varied sizes were investigated based on quantum mechanics (QM) calculations. Moreover, molecular dynamics (MD) simulations were implemented to evaluate mechanical moduli and intermolecular dynamics of TiO2 QDs modified asphalt with different quantum sizes and concentrations. The results from QM calculations unveil that as size of TiO2 QDs rises from 6 Å to 12 Å, energy gap and binding energy of TiO2 QDs decreases by 0.928 eV and 526.38 eV, respectively while density of state (DOS) and absorption coefficient of TiO2 QDs increases. Besides, the results from MD simulations reveal that quantum size imposes significant impact on mechanical moduli of modified asphalt while concentration of TiO2 QDs brings notable influence on interaction between quantum dots and asphalt. Specifically, as concentration of QDs rises from 10 % to 30 %, cohesive energy density (CED) and solubility parameter (SP) of modified asphalt is improved by up to 457 % and 136 %, respectively. With increasing quantum size, bulk modulus, shear modulus, and Young’s modulus of modified asphalt is enhanced by up to 372 %, 206 % and 24 %, respectively. The outcomes of this study provide insights into formula and application of advanced asphalt pavement with TiO2 QDs.

Polaron engineering promotes NIR-II absorption of carbon quantum dots for bioimaging and cancer therapy.

Recent years have witnessed a surge of interest in tuning the optical properties of organic semiconductors for diverse applications. However, achieving control over the optical bandgap in the second near-infrared (NIR-II) window has remained a major challenge. To address this, here we report a polaron engineering strategy that introduces diverse defects into carbon quantum dots (CQDs). These defects induce lattice distortions resulting in the formation of polarons, which can absorb the near-field scattered light. Furthermore, the formed polarons in N-related vacancies can generate thermal energy through the coupling of lattice vibrations, while the portion associated with O-related defects can return to the ground state in the form of NIR-II fluorescence. On the basis of this optical absorption model, these CQDs have been successfully applied to NIR-II fluorescence imaging and photothermal therapy. This discovery could open a promising route for the polarons of organic semiconductor materials as NIR-II absorbers in nanomedical applications.

New PMMA-InP/ZnS nanohybrid coatings for improving the performance of c-Si photovoltaic cells

Abstract Luminescent down-shifting (LDS) nanohybrid films are considered a potential solution to match the absorption spectrum of photovoltaic (PV) cells with the AM1.5 solar spectrum. LDS films were prepared by spin-coating polymethyl methacrylate (PMMA) doped with indium phosphide/zinc sulfide (InP/ZnS) quantum dots (QDs). The effect of doping concentration was investigated using X-ray diffraction, thermogravimetric analysis, transmission, and fluorescence spectroscopy. The results demonstrated that all PMMA LDS nanohybrid films were amorphous and exhibited thermal and chemical stability for all the doping concentrations of QDs. The optimal doping concentration was 0.06 wt%, demonstrating a tunable emission of the highest fluorescence quantum yield of 92% and the lowest reabsorption effect. This film showed the maximum enhancement of the efficiency of c-Si PV cells by 24.28% due to the down-conversion of ultraviolet A (UVA) portion of solar spectrum (320–400 nm) to match the sensitivity of c-Si PV cells. The implications of these results are significant for advancing affordable and clean energy in alignment with important sustainable development goals.

P‐151: The Optimization of Quantum‐Dots Color Filter for Flexible Display Applications

This paper introduces a flexible and uniformly‐dispersed quantum dot (QD) color filter (QDCF) fabricated for micro‐LED by photolithography. We studied the condition of PET films and concentration of QDs, the optimized QDCF exhibited high quantum yield (QY) up to over 70%, and a high optical density (OD) over 1.2. The QY increased and then decreased with the increase of the concentration.

P‐146: Research on Optical Model of Quantum Dot Color Conversion and Blue Backlight Device Architecture

Due to its high quantum yield and unique spectral characteristics, quantum dots (QDs) color conversion materials have attracted great attention in the application of luminescent display products. However, there is a lack of effective optical model for QD color conversion materials, especially for the propagation and distribution of light, when the QD ink contains scattering particles. In this paper, a full‐view optical model of QD conversion and blue backlight device architecture is established. The model can not only output the spectral information in the front view, but also predict the spectral information of the QD color conversion device in other different views. At the same time, the effects of QD concentration, thickness, particle size and refractive index on the luminous efficiency of the device structure are also studied by using this optical model. On the other hand, the influence of conversion efficiency of QD and EL backlight on the power consumption and lifetime of QD products is also studied by using this optical model. The model can realize the output of the optical influence on the future products by the parameters related to QD color conversion materials and backlight without actual device fabrication, which can greatly reduce time and labor cost.

Two-photon absorption in quantum dots with Hellmann potential

Abstract We study the nonlinear optical absorption properties of a spherical quantum dot (SQD) with Hellmann potential, focusing on the two-photon absorption (TPA) process, using GaAs/AlGaAs material as an example. The radial Schrödinger equation is solved using the Nikiforov-Uvarov method, while the two-photon absorption coefficient is determined through second-order perturbation theory concerning the electron-photon interaction. Our study shows that the intraband transition has a smaller energy transition than the interband transition, leading to TPA spectra for the intraband transition that is restricted within a smaller energy range and exhibits a higher peak value than those for the interband transition. The peak corresponding to the orbital quantum number of electrons in SQD ℓ = 2 consistently appears to the left of the peak corresponding to ℓ = 1 in both intraband and interband transition cases. Additionally, the dependence of the absorption peak position on the order of transition, n, differs between intra- and inter-band transitions. We also observe blue shift behavior in the TPA spectra as all three parameters, r 0, V 0e , and η, increase. Our investigation has the potential to enable the design of novel photonic devices, ultra-fast optical switches, and highly efficient solar cells through the optimization of quantum dot material properties.

Fluorescence Enhancement of CdS:Ag Quantum Dots Co-Assembled with Au Nanoparticles in a Hollow Nanosphere Form.

Colloidal quantum dots (QDs) have exceptional fluorescence properties. Overcoming aggregation-induced quenching and enhancing the fluorescence of colloidal QDs have remained a challenging issue in this field. In this study, composite hollow nanospheres composed of Au nanoparticles (NPs) and CdS:Ag-doped QDs were successfully constructed through controlled microemulsion-based cooperative assembly. This method harnessed the localized surface plasmon resonance (LSPR) effect of Au NPs nearby doped QDs, resulting in enhanced doped QD fluorescence and the observation of the Purcell effect. The composite hollow nanospheres show a fluorescence enhancement compared to that of the pure CdS:Ag QDs. The enhanced fluorescence was demonstrated to come from the synergetic enhancement of the absorption and emission transition of the doped QDs. This approach provides a feasible technological pathway to address the challenge of improving the fluorescence performance of the doped QDs.

Brilliant quantum dots’ photoluminescence from a dual-resonance plasmonic grating

Semiconductor quantum dots (QDs) have recently caused a stir as a promising and powerful lighting material applied in real-time fluorescence detection, display, and imaging. Photonic nanostructures are well suited for enhancing photoluminescence (PL) due to their ability to tailor the electromagnetic field, which raises both radiative and nonradiative decay rate of QDs nearby. However, several proposed structures with a complicated manufacturing process or low PL enhancement hinder their application and commercialization. Here, we present two kinds of dual-resonance gratings to effectively improve PL enhancement and propose a facile fabrication method based on holographic lithography. A maximum of 220-fold PL enhancement from CdSe/CdS/ZnS QDs are realized on 1D Al-coated photoresist (PR) gratings, where dual resonance bands are excited to simultaneously overlap the absorption and emission bands of QDs, much larger than those of some reported structures. Giant PL enhancement realized by cost-effective method further suggests the potential of better developing the nanostructure to QD-based optical and optoelectronic devices.

Maximization of cytochrome C oxidase enzyme activity by optimizing color conversion from red organic light-emitting diodes

Photobiomodulation (PBM) therapy using red and near-infrared (NIR) light can effectively activate cytochrome C oxidase (CCO) enzyme to promote wound healing in living organisms. To maximize this therapeutic effect, the use of a light source with a spectrum absorbed by the CCO enzyme is necessary. A red/NIR light source optimized for CCO enzyme was obtained by partially color-converting a red organic light-emitting diode with copper indium sulfide/zinc sulfide quantum dots (QDs). To increase color conversion efficiency, the dispersion of QDs was improved by using a fibrous color conversion layer (FCCL). By optimizing the QD content in the FCCL, a red/NIR light source similar to the absorption spectrum of CCO enzyme was obtained with a spectral matching ratio of 81.7 %. When this light source was used in PBM therapy, it was experimentally verified that it showed a much faster wound closure effect compared to general red light, and it was proven that this was due to increased activity of the CCO enzyme. This study is a method of obtaining a red/NIR light source for PBM suitable for a specific enzyme performing a specific function, and is particularly useful due to its excellent form factor of being large, thin, and flexible.

Polyvalent Aptamer-Functionalized NIR-II Quantum Dots for Targeted Theranostics in High PD-L1-Expressing Tumors.

Ag2S quantum dots (QDs) show superior optical properties in the NIR-II region and display significant clinical potential with favorable biocompatibility. However, inherent defects of low targeting and poor solubility necessitate practical modification methods to achieve the theranostics of Ag2S QDs. Herein, we used rolling circle amplification (RCA) techniques to obtain long single-stranded DNA containing the PD-L1 aptamer and C-rich DNA palindromic sequence. The C-rich DNA palindromic sequences can specifically chelate Ag2+ and thus serve as a template to result in biomimetic mineralization and formation of pApt-Ag2S QDs. These QDs enable specific targeting and illuminate hot tumors with high PD-L1 expression effectively, serving as excellent molecular targeted probes. In addition, due to the high NIR-II absorption of Ag2S QDs, pApt-Ag2S QDs exhibit remarkable photothermal properties. And besides, polyvalent PD-L1 aptamers can recognize PD-L1 protein and effectively block the inhibitory signal of PD-L1 on T cells, enabling efficient theranostics through the synergistic effect of photothermal therapy and immune checkpoint blocking therapy. Summary, we enhance the biological stability and antibleaching ability of Ag2S QDs using long single-stranded DNA as a template, thereby establishing a theranostic platform that specifically targets PD-L1 high-expressing inflamed tumors and demonstrates excellent performance both in vitro and in vivo.