Figure - available via license: CC BY
Content may be subject to copyright.
(a) Photoluminescence emission spectra of CdSe/ZnS QDs before and after being molecularly linked by 1,4-benzenedimethanethiol (molar ratio of ligands to QDs: 1/7). (b) Photoluminescence emission spectra of molecularly linked CdSe/ZnS QDs with increasing concentration of 1,4-benzenedimethanethiol (molar ratio of ligands to QDs: 1/7, 1/2, 2/1, resp.).
Source publication
The colloidal photoluminescent quantum dots (QDs) of CdSe (core) and CdSe/ZnS (core/shell) were synthesized at different temperatures with different growth periods. Optical properties (i.e., UV/Vis spectra and photoluminescent emission spectra) of the resulting QDs were investigated. The shell-protected CdSe/ZnS QDs exhibited higher photoluminescen...
Similar publications
AgInS2 nanoparticles of various sizes were synthesized over a range of reaction temperature from 120 to 180 degrees C. The band gap energies, obtained directly from photoluminescence spectra for the first time, were well correlated to the quantum confinement effects as a function of nanoparticle size, because the band gap shift was explained by the...
Cadmium-sulfide nanocrystals are produced by the colloidal method. Doping with zinc and copper is conducted during nanocrystal growth. The optical absorption and photoluminescence spectra are studied. The maximum concentration of the optically active copper impurity is determined from a shift of the fundamental absorption edge to lower energies. It...
Eu3+ doped nanocomposite containing In2O3 quantum dots (QDs) was successfully fabricated by a melt quenching technique. The crystallization process of cubic In2O3 phase was revealed by X-ray diffraction and transmissions electron microscopy. The size of In2O3 QDs can be well tuned by adjusting treatment duration and a size-tunable In2O3 emission wa...
We report for the first time the synthesis of quasi-two-dimensional (2D) perovskite nanoplates by incorporating 2D TMA
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>
PbBr
<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>
(C
<sub xmlns:mml="h...
The present paper presents a straightforward method for producing thin film layers of sulfide quantum dots (PbS-QDs) on a glass substrate using chemical solution deposition (CSD) assisted by dipcoating technique. The deposited PbS-QDs films were subjected to a comprehensive analysis using atomic force microscopy (AFM), energy dispersive X-ray (EDX)...
Citations
... Moreover, to obtain specificity of NMs in their sensing action, the surface modification, called functionalization, must be applied first. 16,17 There are several methods for detecting an analyte with NPs, e.g., emission quenching from NPs, increase in NPs' emission due to passivation of the NPs' surface by the analyte, and nonradiative Forster resonance energy transfer (FRET). 18 Nanostructured materials with great potential for the easy identification of individual chemical compounds with minimized sample volumes and their treatment are particularly promising in the process of biosensors development. ...
The study of neurotransmitters and stress hormones allows the determination of indicators of the current stress load in the body. These species also create a proper strategy of stress protection. Nowadays, stress is a general factor that affects the population, and it may cause a wide range of serious disorders. Abnormalities in the level of neurohormones, caused by chronic psychological stress, can occur in, for instance, corporate employees, health care workers, shift workers, policemen, or firefighters. Here we present a new nanomaterials-based sensors technology development for the determination of neurohormones. We focus on fluorescent sensors/biosensors that utilize nanomaterials, such as quantum dots or carbon nanomaterials. Nanomaterials, owing to their diversity in size and shape, have been attracting increasing attention in sensing or bioimaging. They possess unique properties, such as fluorescent, electronic, or photoluminescent features. In this Review, we summarize new trends in adopting nanomaterials for applications in fluorescent sensors for neurohormone monitoring.
... This type of QDs has previously been functionalized using various types of thiol molecules. The most efficient molecules, that also improved their optical properties were 1,4benzenedimethanethiol (1,4-BDMT), biphenyl-4,4′-dithiol, 1,16-hexadecanedithiol, 1,11-undecanedithiol, 1,8octanedithiol, and 11-mercapto-1-undecanol (Zhu et al., 2014). Another simple functionalization method for CdSe QDs is through the use of mercaptopropyl acid (MPA) and surface passivation by introducing a ZnS shell. ...
LFIA is one of the most successful analytical methods for various target molecules detection. As a recent example, LFIA tests have played an important role in mitigating the effects of the global pandemic with SARS-COV-2, due to their ability to rapidly detect infected individuals and stop further spreading of the virus. For this reason, researchers around the world have done tremendous efforts to improve their sensibility and specificity. The development of LFIA has many sensitive steps, but some of the most important ones are choosing the proper labeling probes, the functionalization method and the conjugation process. There are a series of labeling probes described in the specialized literature, such as gold nanoparticles (GNP), latex particles (LP), magnetic nanoparticles (MNP), quantum dots (QDs) and more recently carbon, silica and europium nanoparticles. The current review aims to present some of the most recent and promising methods for the functionalization of the labeling probes and the conjugation with biomolecules, such as antibodies and antigens. The last chapter is dedicated to a selection of conjugation protocols, applicable to various types of nanoparticles (GNPs, QDs, magnetic nanoparticles, carbon nanoparticles, silica and europium nanoparticles).
... [7] Surface modification methods, such as polymer encapsulation, surface grafting, and ligand exchange, can improve the PLQE of the QDs up to 30% due to better packing of the QD surface and passivation of the PL quenching defects. [66,67] Another solution for the poor PLQE of QDs is the shelling of inorganic atomic layers with a wider bandgap on the surface of core QDs, which enhances the PLQE by effectively reducing the nonradioactive recombination. [68] Although the PLQE of core-only QDs has been reported to be lower than 50%, the best reported values of PLQE are around 80% for inorganic-shelled QDs, which is competitive with organic species. ...
We present a comprehensive numerical framework for the electrical and optical modeling and simulation of hybrid quantum dot light-emitting diodes (QD-LEDs). We propose a model known as hopping mobility to calculate the carrier mobility in the emissive organic layer doped with quantum dots (QDs). To evaluate the ability of this model to describe the electrical characteristics of QD-LEDs, the measured data of a fabricated QD-LED with different concentrations of QDs in the emissive layer were taken, and the corresponding calculations were performed based on the proposed model. The simulation results indicate that the hopping mobility model can describe the concentration dependence of the electrical behavior of the device. Then, based on the continuity equation for singlet and triplet excitons, the exciton density profiles of the devices with different QD concentrations were extracted. Subsequently, the corresponding luminance characteristics of the devices were calculated, where the results are in good agreement with the experimental data.
... The use of thiol molecules as capping agents is seen to enhance the optical properties of core-shell CdSe/ZnS QDs (ZHU et al., 2014). Further, the fluorescence quantum yields of CdSe and CdTe nanocrystals is observed to be greatly influenced by the capping of their surfaces with thiol molecules (WUISTER et al., 2004). ...
... This can not only explain that the dependence of photocatalytic activity, but also on the transfer rate and separation efficiency of the photogenerated charges as well as improved surface chemistry characteristics of the photocatalyst. Fig. 9(a) and (b) shows the PL spectra of the prepared ZnS and NiO photocatalysts at excitation wavelengths of 380 nm and 290 nm, respectively (Ding et al., 2018;Karthikeyan et al., 2016;Poornaprakash et al., 2013;Siddique et al., 2018;Uddandarao et al., 2019;Zhu et al., 2014). The normalized PL intensities are found to decrease in the orderof NiO > ZnS > ZCNS (Fig. 9(c)), which is in good agreement with the change in photocatalytic activity. ...
Design and development of the efficient and durable photocatalyst that generates H2 fuel utilizing industrial wastewater under solar light is a sustainable process. Innumerable photocatalysts have been reported for efficient hydrogen production, but their large-scale production with the same efficiency of hydrogen production is a challenging task. In this study, a few gram-scale syntheses of ZnS wrapped with NiO hierarchical core-shell nanostructure via the surfactant-mediated process has been reported. Morphology and crystal structure analysis of ZnS/NiO showed spherical shaped hierarchical core-shell with cubic and face-centered cubic crystal structures. The surface examination confirmed the presence of Zn2+, S2-, Ni2+ and O2- ions in the nanocomposite. The photocurrent and photo-luminescence studies of pristine and nanocomposites revealed that core-shell material is non-corrosive with a prolonged life-time of photo-excitons. Parametric studies on photocatalytic H2 generation in lab-scale photoreactor using crude glycerol in water recorded a high rate of H2 generation of 9.3 mmol.h-1.g-1 of catalyst under the simulated solar light irradiation. Optimized reaction parameters are extended to a demonstrative photoreactor containing aqueous crude glycerol produced 18.5 mmol.h-1 of H2 generation under the natural solar light irradiation. The same nanostructures were further tested with the simulated sulfide wastewater and the optimized catalyst showed H2 production of 350 mL.h-1. The experimental results of time-on stream and catalytic stability demonstrated that ZnS/NiO hierarchical core-shell nanostructures can be recyclable and reusable for the continuous photocatalytic H2 generation.
... A) showed that the absorption intensity of colloidal CdSe QDs increased with the concentration of MAA ligands. Moreover, the first absorption peak had a slight redshift, which corresponded to the change of PL spectra after complexing with thiol ligands.34 The schematic diagram inFigure 2(A) explained that the surface metal cations coordinating with thiols affected the electronic structure of colloidal CdSe QDs. ...
... The schematic diagram inFigure 2(A) explained that the surface metal cations coordinating with thiols affected the electronic structure of colloidal CdSe QDs. To some extent, the first absorption peak shift mainly depended on the diameter of QDs.30,34 The slight redshift was mainly due to the change of the surface envi-ronment of the MAA ligands, leading to the radiation recombination of the defect band gap and reducing the non-radiation recombination. ...
Cadmium selenide (CdSe) quantum dots (QDs) is a promising semiconductor and fluorescence nanocrystal with quantum size effect. To address the problem of fluorescence emission during the process of the ligand transformation of colloidal cluster CdSe QDs from nonpolar organic solvents to polar inorganic aqueous solutions, the surface ligand exchange with mercapto acetic acid (MAA) was proposed. It was attributed to the Cd‐O bond breaking and the Cd‐S bond formation. The intensity and wavelength of fluorescence emission spectra could be adjusted by controlling the concentration of MAA. The photoluminescence (PL) spectra and UV‐Vis absorption spectra of colloidal cluster CdSe QDs indicated that the electronic properties of the interface varied with the exchange of the surface ligands. Moreover, the band‐edge emission quenching occurred and the maximum redshift of the PL spectrum could reach 28 nm. The enhancement of the deep trap emission peaks of CdSe QDs appeared in 600‐900 nm region, and the maximum blue shift of the defect peak in PL spectrum could reach 80 nm with the increase concentration of MAA. The absorption spectra and PL spectra on the surface of porous alumina thin film were used to further analyze the charge separation and capture of charge carriers. This novel organic‐inorganic ligand exchange method provides an effective strategy for regulating fluorescence and electron transfer, which could be used on biological, solar cells or other practical applications.
... Two different coatings were selected based on synthesis reproducibility and yield. Specifically, the relatively simple thioglycolic acid, consisting of a short organic chain presenting both thiol and carboxylic acid functional groups (TGA, Zhu et al., 2014) was compared to the more complex organic polymer poly(maleic anhydride-alt-1-octadecene) (POAMA, Pellegrino et al., 2004). According to Faucher et al. (2018), the QDs are expected to have a CdS gradient between the CdSe core and the ZnS shell whereas the yellowish color and fluorescence emission in the green portion of the visible spectra indicated NPs diameter of 7 nm, with core size of circa 3.4 nm. ...
The increasing application of Quantum Dots (QDs) is cause of concern for the potential negative effects for the ecosystem, especially in soils that may act as a sink. In this study, soil leaching experiments were performed in quartz sand packed columns to investigate the behavior of core-shell CdSe/ZnS QDs coated with either small ligands (TGA-QDs) or more complex polymers (POAMA-QDs). Fluorescence emission was compared to mass spectrometric measurements to assess the nanoparticles (NPs) state in both the leachate (transported species) and porous media (deposited amounts). Although both QDs were strongly retained in the column, large differences were observed depending on their capping ligand stability. Specifically, for TGA-QDs elution was negligible and the retained fraction accumulated in the top-columns. Furthermore, 74% of the NPs were degraded and 38% of the Se was found in the leachate in non-NPs state. Conversely, POAMA-QDs were recovered to a larger extent (78.1%), and displayed a higher transport along the soil profile. Further experiments with altered NPs showed that homo-aggregation of the QDs prior injection determined a reduced mobility but no significant changes in their stability. Eventually, ageing of the NPs in the column (15 days) caused the disruption of up to 92% of the original QDs and the immobilization of NPs and metals. These results indicate that QDs will accumulate in top-soils, where transformations phenomena will determine the overall transport, persistency and degradation of these chemicals. Once accumulated, they may act as a source for potentially toxic Cd and Se metal species displaying enhanced mobility.
... The use of QDs for sensors construction requires adjusting their optical properties adequately to the needs that arise their shape, size, the color of emission, position of the absorption band. Moreover, to get specificity of QDs in their sensing action, the surface modification-called functionalizationmust be applied first [22,23]. Functionalization is the process of attaching, exchanging already attached chemical molecules present on the surface of quantum dots. ...
... The use of QDs for sensors construction requires adjusting their optical properties adequately to the needs that arise their shape, size, the color of emission, position of the absorption band. Moreover, to get specificity of QDs in their sensing action, the surface modification-called functionalization-must be applied first [22,23]. Functionalization is the process of attaching, exchanging already attached chemical molecules present on the surface of quantum dots. ...
Fundamentals of quantum dots (QDs) sensing phenomena show the predominance of these fluorophores over standard organic dyes, mainly because of their unique optical properties such as sharp and tunable emission spectra, high emission quantum yield and broad absorption. Moreover, they also indicate no photo bleaching and can be also grown as no blinking emitters. Due to these properties, QDs may be used e.g., for multiplex testing of the analyte by simultaneously detecting multiple or very weak signals. Physico-chemical mechanisms used for analyte detection, like analyte stimulated QDs aggregation, nonradiative Förster resonance energy transfer (FRET) exhibit a number of QDs, which can be applied in sensors. Quantum dots-based sensors find use in the detection of ions, organic compounds (e.g., proteins, sugars, volatile substances) as well as bacteria and viruses.
... Recently, new advanced preparation techniques offer an opportunity to fabricate several-nanometer-length magnetic particles with narrow size distributions and different compositions through a variety of procedures, either embedded in a solid matrix or diluted in organic solvents. Depending on the material and structural synthesis, different types of MNP systems have been developed, for example, Janus NPs [34,49,50], core-shell [51,52], dumbbell [53,54], flower [55][56][57], dimers/trimers [58][59][60], and multicomponent hybrid types of nanostructures [59,[61][62][63][64] called multifunctional MNPs. Jointly, these bifunctional MNPs manifest unique combinations of magnetic and optical/plasmonic/electronic properties and have shown great potential for different applications [64]. ...
Multifunctional magnetic nanostructures have been appealing in nanoscience owing to their manifold importance in the superfluity of electronic devices and biomedical applications. The integration of multiple discrete functionalities of two or more nanoparticles in a single hybrid system with different types of structures leads to diverse execution capabilities in, for example, catalysis, magnetic sensors, magnetic read heads, and storage devices. These hybrid systems require a theoretical approach to realize their various unknown characteristics. This chapter presents a brief introduction to multifunctional complex magnetic nanostructures, their synthesis and characterization techniques, along with important applications in the magnetic sector. The major focus is on core-shell and dumbbell nanoparticles. Progress in theoretical models to explain complex magnetic phenomena is also discussed.
... 50,51 Their versatility for bioconjugation with various biomolecules and imaging advantages make QDs outshine other nanocarriers. 52,53 However, the major drawback of QDs lies within their toxicity and excretion pathway. Studies have shown that their toxicity is very much dependent on their core-shell material, bioconjugation and surface functionalization. ...
Breast cancer is the most common malignancy worldwide, especially among women, with substantial after-treatment effects. The survival rates of breast cancer have decreased over the years even with the existence of various therapeutic strategies, specifically, chemotherapy. Clinical drugs administered for breast cancer appear to be non-targeting to specific cancer sites leading to severe side effects and potentially harming healthy cells instead of just killing cancer cells. This leads to the need for designing a targeted drug delivery system. Nanomaterials, both organic and inorganic, are potential drug nanocarriers with the ability of targeting, imaging and tracking. Various types of nanomaterials have been actively researched together with their drug conjugate. In this review, we focus on selected nanomaterials, namely solid-lipid, liposomal, polymeric, magnetic nanoparticles, quantum dots, and carbon nanotubes and their drug conjugates, for breast cancer studies. Their advantages, disadvantages and previously conducted studies were highlighted.
