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Photosensitive quantum dot light‐emitting diodes (PSQLEDs) possess the dual capabilities of generating and detecting light signals, which is of significant importance for the development of miniaturized and integrated optoelectronic devices. However, the state‐of‐the‐art PSQLEDs can only detect light signals within a certain wavelength range, and require switching between the two functions under different bias voltage directions. In this work, The use of a ZnO/quantum dots (QDs)/ZnO multilayer (ZQZ ML) architecture as both the electron transport layer and the photosensitive layer is pioneered. The QDs in this structure are composed of narrow‐bandgap lead sulfide QDs and wide‐bandgap cadmium selenide QDs, successfully realizing a unique PSQLED device with C photosensitive characteristics. As a result, the as‐fabricated device can respond to illumination from 365 to 1300 nm, and the device achieves a photoresponse rate of 20.9 mA W−1 in self‐powered mode to UV light. After UV light irradiation, the maximum external quantum efficiency and maximum luminance of device reached 11.8% and 64,549 cd m−2, respectively. The device shows a record‐high luminance ON/OFF ratio of 5500%, which is beneficial for high contrast and accurate information display. [ABSTRACT FROM AUTHOR]

Despite the promising applications of the use of quantum dots (QDs) in the biomedical field, the long-lasting effects of QDs on the cell remain poorly understood. To comprehend the mechanisms underlying the toxic effects of QDs in yeast, we characterized defects associated with receptor-mediated endocytosis (RME) as well as pinocytosis using Saccharomyces cerevisiae as a model in the presence of cadmium selenide/zinc sulfide (CdSe/ZnS) QDs. Our findings revealed that QDs led to an inefficient RME at the early, intermediate, and late stages of endocytic patch maturation at the endocytic site, with the prolonged lifespan of GFP fused yeast fimbrin (Sac6-GFP), a late marker of endocytosis. The transit of FM1-43, a lipophilic dye from the plasma membrane to the vacuole, was severely retarded in the presence of QDs. Finally, QDs caused an accumulation of monomeric red fluorescent protein fused carbamoyl phosphate synthetase 1 (mRFP-Cps1), a vacuolar lumen marker in the vacuole. In summary, the present study provides novel insights into the possible impact of CdSe/ZnS QDs on the endocytic machinery, enabling a deeper comprehension of QD toxicity. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are widely used in optoelectronics, lighting, and photovoltaics leading to their potential release into the environment. The most promising alternative to the highly toxic cadmium selenide (CdSe) QDs are indium phosphide (InP) QDs, which show reduced toxicity and comparable optical and electronic properties. QD degradation leads to the release of toxic metal ions into the environment. Coating the QD core with robust shell(s) composed of another semi-conductor material enhances their properties and protects the QD from degradation. We recently developed double-shelled InP QDs, which proved to be less toxic than single-shell QDs. In the present study, we confirm their reduced cytotoxicity, with an LC50 at 77 nM for pristine gradient shell QDs and >100 nM for pristine thin and thick shell QDs. We also confirm that these three QDs, when exposed to simulated sunlight, show greater cytotoxicity compared to pristine ones, with LC50 ranging from 15 to 23 nM. Using a combination of spectroscopic and microscopic techniques, we characterize the degradation kinetics and transformation products of single- and double-shell QDs, when exposed to solar light at high temperature, simulating environmental conditions. Non-toxic pristine QDs degrade to form toxic In–phosphate, In–carboxylate, Zn–phosphate, and oxidized Se, all of which precipitate as heterogeneous deposits. Comparison of their degradation kinetics highlights that the QDs bearing the thickest ZnS outer shell are, as expected, the most resistant to photodegradation among the three tested QDs, as gradient shell, thin shell, and thick shell QDs lose their optical properties in less than 15 min, 60 min, and more than 90 min, respectively. They exhibit the highest photoluminescence efficiency, i.e., the best functionality, with a photoluminescence quantum yield in aqueous solution of 24%, as compared to 18% for the gradient shell and thin shell QDs. Therefore, they can be considered as safer-by-design QDs. [ABSTRACT FROM AUTHOR]

Constructing photocatalysts to promote hydrogen evolution and carbon dioxide photoreduction into solar fuels is of vital importance. The design and establishment of an S-scheme heterojunction system is one of the most feasible approaches to facilitate the separation and transfer of photogenerated charge carriers and obtain powerful photoredox capabilities for boosting photocatalytic performance. Herein, a zero-dimensional/one-dimensional S-scheme heterojunction composed of CdSe quantum dots and polymeric carbon nitride nanorods (CdSe/CN) is created and constructed via a linker-assisted hybridization approach. The CdSe/CN composites exhibit superior photocatalytic activity in water splitting and promoted carbon dioxide conversion performance compared with CN nanorods and CdSe quantum dots. The best efficiency in photocatalytic water splitting (10.2% apparent quantum yield at 420 nm irradiation, 20.1 mmol g−1 h−1 hydrogen evolution rate) and CO2 reduction (0.77 mmol g−1 h−1 CO production rate) was achieved by 5%CdSe/CN composites. The significantly improved photocatalytic reactivity of CdSe/CN composites primarily originates from the emergence of an internal electric field in the zero-dimensional/one-dimensional S-scheme heterojunction, which could greatly improve the photoinduced charge-carrier separation. This work underlines the possibility of employing polymeric carbon nitride nanostructures as appropriate platforms to establish highly active S-scheme heterojunction photocatalysts for solar fuel production. [ABSTRACT FROM AUTHOR]

In this study, dielectric and electro-optic properties of 4-pentyl-4′-cyanobiphenyl (5CB) nematic liquid crystal (LC) and different concentrations of nickel (II) phthalocyanine (Ni(II)Pc) and cadmium selenide sulfide/zinc sulfide (CdSeS/ZnS) quantum dot (QD)-doped LC have been investigated in dark and ultraviolet (UV) illumination. Some important dielectric parameters such as the real and imaginary part of the complex dielectric constant (ε′ and ε′′), relaxation frequency (fR), and relaxation time (τ) have been determined. The output of the study shows that Ni(II)Pc and CdSeS/ZnS contribution and UV illumination improved the dielectric properties. Optical band gap (Egap) values of all samples have been obtained using the UV spectroscopy technique. The Egap value decreased after dispersion of Ni(II)Pc and CdSeS/ZnS in the pure LC. The results may be beneficial for the design of new optoelectronic devices. [ABSTRACT FROM AUTHOR]

The origin of the ubiquitous low-frequency shoulder on the longitudinal optical (LO) phonon fundamental in the Raman spectra of CdSe quantum dots is examined. This feature is usually assigned as a "surface optical" (SO) phonon, but it is only slightly affected by modifying the surface through exchanging ligands or adding a semiconductor shell. Here we present excitation profile data showing that the low-frequency shoulder loses intensity as the excitation is tuned to longer wavelengths, closer to resonance with the lowest-energy 1Se-1S3/2 excitonic transition. Calculations of the resonance Raman spectra are carried out using a fully atomistic model with an empirical force field to calculate the phonon modes and the standard effective mass approximation envelope function model to calculate the electron and hole wave functions. When a force field of the Tersoff type is used, the calculated spectra closely resemble the experimental ones in showing mainly the higher-frequency LO phonon with 1Se-1S3/2 resonance but showing intensity in lower-frequency features with 1Pe-1P3/2 resonance. These calculations indicate that the main LO phonon peak involves largely motion of the interior atoms, while the low-frequency shoulder is more equally distributed throughout the crystal but not surface-localized. Interestingly, very different results are obtained with the widely used Coulomb plus Lennard-Jones force field developed by Rabani, which predicts far more disordered structures and more localized phonon modes for the nanocrystals compared with the Tersoff-type potential.

This paper describes our research into phase transition, electro-optical and dielectric behaviors of polymer dispersed liquid crystal (PDLC) and cadmium selenide sulphide/zinc sulphide quantum dot (QD) doped PDLC (PDLC/QD). The PDLC was prepared with nematic liquid crystal (E63) and UV-curable photopolymer (NOA65) by using a polymerization induced phase separation technique. Dielectric properties of composites were investigated with a dielectric/impedance analyzer at 1 kHz–10 MHz frequency range. Electro-optical measurements of investigated samples were carried out using an electro-optical switching method. Phase transition temperature of PDLC and PDLC/QD composites was also determined, using a differential scanning calorimeter. The results showed that the introduction of QD significantly changes the physical properties of PDLC, and these changes could become a focus of interest for future applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • CdSe quantum dots tested as fuel markers for diesel oil. • Nanocrystals produced by one step colloidal growth in hexadecane. • Nanomarker detected either by electronic absorption or fluorescence spectroscopy. • Fluorescent nanoparticles detected down to 1 mg/kg level. Abstract Markers are regularly used to detect fraud and adulteration in fuel as well as to track products in a distribution chain. Herein, we tested the use of CdSe semiconductor fluorescent nanocrystals, quantum dots, as a new class of fuel markers. Quantum dots show bright fluorescence and they can be excited by light sources covering a broad spectral range, from ultraviolet up to the near infrared region. This class of markers presents great advantages over conventional ones, such as high detectability potential, fluorescence emission in multicolor wavelengths, high photostability, and easy preparation procedures. In this work, we prepared CdSe quantum dots by colloidal controlled growth in an organic medium to be used for evaluation of diesel oil. The detection method was either by electronic absorption or fluorescence spectroscopies. The nanomarkers could be detected down to 1 mg/kg level in diesel fuel. The overall results indicated that CdSe quantum dots have the potential for use as a new class of fuel nanomarkers. [ABSTRACT FROM AUTHOR]

Abstract The growing interest on the use of colloidal Quantum Dots (QDs) in scintillation and dosimetry applications in comparison with organic fluorophores relies in their narrower and tunable photoluminescence (PL) emission, easier chemical processability and higher cross-section for ionizing radiation. In this context, a deep understanding of the role of the embedding medium on the QD optical properties in unirradiated and irradiated samples represents an important issue. In this paper, we present the optical characterization of colloidal core-shell CdSe/ZnS QDs embedded in polyvinyl alcohol (PVOH) and irradiated with 2 MeV protons at different fluences. The characterization of the samples, performed by both steady-state and time-resolved PL measurements, indicates a damage of the QDs at the lowest fluence (1013 H+cm−2), demonstrated by a quenching of the QD PL intensity and by a shortening of the QD lifetime. At the middle fluence (5 × 1013 H+cm−2) a partial recovering of the QD optical properties are observed, due to energy transfer phenomena between radiation-induced PL defects in the PVOH, acting as donors, and the QDs, acting as acceptors. The higher concentration of PVOH PL defects in the most irradiated sample (1014 H+cm−2) led to an enhancement of the QD PL intensity in comparison with the unirradiated sample, highlighting the crucial role of the embedding medium in the post-irradiation QD optical response. Highlights • The QD embedding medium has an important role on the irradiated QD optical response. • At the fluence of 1013 H+cm−2, QD PL intensity and lifetime decrease. • At the fluence of 5 × 1013 H+cm−2, QD PL intensity and lifetime are partly recovered. • At the fluence of 1014 H+cm−2, QD PL intensity and lifetime are enhanced. • Energy transfer phenomena arise between PVOH photoluminescent defects and QDs. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a molecularly imprinted polymer (MIP)‐fluorescent probe based on hydrophobic CdSe/ZnS quantum dots (CdSe/ZnS@MIP) was designed and synthesized by bulk polymerization for detecting methamidophos (MAP). The CdSe/ZnS@MIP was characterized by Fourier‐transform infrared spectroscopy, thermo‐gravimetric analysis and adsorption properties, and it exhibited good adsorption capacity and fluorescent stability, and excellent selectivity. Under optimal conditions, the fluorescence showed a good linear decrease in the range of 3.50 × 10−7–0.71 × 10−3 mol/L with a correlation coefficient of 0.995. The limit of detection of the fluorescent probe was 9.16 × 10−8 mol/L, and the relative standard deviation of the method for nine replicate analyses of 4.0 × 10−6 mol/L MAP was 4.1%. Apple and pear samples spiked with MAP at three levels were extracted and determined by the presented method with good recoveries (89.7%–94.9%). The accuracy of the method was verified by gas chromatography for the detection of kidney beans, leek and cucumber samples, and no significant difference was observed for the results of two methods. [ABSTRACT FROM AUTHOR]

We present a simple experimental procedure to obtain CdSe quantum dots from aqueous solution with a controllable size. Double-hydrophilic block copolymers consisting of a poly(ethylene glycol) block and a block of either poly(ethylene imine) or polylysine are used as stabilizers. UV/VIS absorption spectroscopy, analytical ultracentrifugation and transmission electron microscopy are used to examine the resulting quantum dots. The particle size can be simply controlled by adjusting the polymer concentration during synthesis for both block copolymers. [ABSTRACT FROM AUTHOR]

Sol gel dip coating method has been used for preparing ZnO nanorods. ZnO nanorods have been sensitized using CdSe quantum dots by simple chemical method. Uniform coverage of quantum dots on ZnO nanorods is observed. The structural, optical and morphology of the ZnO nanorods, CdSe quantum dots and CdSe quantum dot sensitized ZnO nanorods have been studied. The presence of CdSe quantum dots in ZnO nanorods based film is clearly seen in FESEM and TEM image and the elements Zn, O, Cd and Se present in the film was confirmed by EDAX analysis. FTO/CdSe quantum dot-ZnO nanorods/electrolyte/platinum structure based solar cell has been fabricated and the cell efficiency has been found to be 2.1%. [ABSTRACT FROM AUTHOR]

Hybrid systems based on graphene and semiconductor quantum dots are prospective materials for optoelectronics and photonics. In this work, electronic structure and dielectric properties of small particles of cadmium sulfide on the surface of graphene were studied using the density functional theory. The optical spectrum of this hybrid structure depends on the orientation of the nanoparticle relative to graphene due to the interaction between electrons of sulfur atoms on the surface of the CdS particle and π-orbitals of carbon atoms. [ABSTRACT FROM AUTHOR]

CdSe nanocrystal (NC) thin films of different NC sizes were synthesized using vacuum deposition technique. The films showed blue shift of band gap and the NC sizes calculated size using Brus equation were 9.40, 9.68 and 9.82 nm. DC conductivity and photoconductivity of as-deposited and annealed films increased and activation energy for conduction decreased with increase in the NC size. Also, both carrier concentration and mobility of the films increased with increase in the size of the NCs which was attributed to the increased electronic coupling between the NCs. The slow response part of photocurrent response pulse analyzed using power law: I ph ∞ t α gave larger values for α for larger NC size indicating stronger electronic coupling between grains in films of larger grain sizes. Charge transport in the CdSe NC films was akin to that of solid films of CdSe quantum dots, of sizes given by Brus equation, connected together by an outer shell of CdSe material where charge carriers had free movement. Additionally, measurement of the characteristics of the hetero-junction formed by the CdSe NC film with a similarly deposited Cu 2 Se film demonstrated usefulness of the CdSe NC films synthesized using the present technique for practical applications. [ABSTRACT FROM AUTHOR]

A novel composite CdSe quantum dots (QDs)-polymer film achieving tri-function of electrochromic, electrofluorescent and light-induced coloration effects was deposited. Combining the advantages of both CdSe QDs and conjugated electrochromic polymers, the composite film presents excellent electrochromic properties with low redox potential, high optical contrast and fast response time. In addition, it achieves enhanced performance that the composite film could switch between non-fluorescent and fluorescent state, in which the photoluminescence (PL) intensity is more than twice that of pristine polymer film. Furthermore, the material can gradually become self-colored from bleached state under the irradiation of sunlight. Therefore, the trifunctional composite film may pave a new way for designing energy-saving electrochromic and electrofluorescent device in the future. [ABSTRACT FROM AUTHOR]

The present study reports the fabrication of CdSe quantum dot (QD)-sensitized photocathodes on NiO-coated indium tin oxide (ITO) electrodes and their H2-generating ability upon light irradiation. A well-established spin-coating method was used to deposit CdSe QD stock solution onto the surface of NiO/ITO electrodes, thereby leading to the construction of various CdSe QD-sensitized photocathodes. The present report includes the construction of rainbow photocathodes by spin-coating different-sized QDs in a sequentially layered manner, thereby creating an energetically favorable gradient for charge separation. The resulting rainbow photocathodes with forward energetic gradient for charge separation and subsequent electron transfer to a solution-based hydrogen-evolving catalyst (HEC) exhibit good light-harvesting ability and enhanced photoresponses compared with the reverse rainbow photocathodes under white LED light illumination. Under minimally optimized conditions, a photocurrent density of as high as 115 μA·cm-2 and a Faradaic efficiency of 99.5% are achieved, which is among the most effective QD-based photocathode water-splitting systems. [ABSTRACT FROM AUTHOR]

CdSe/ZnTe core shell nanoparticles present original optical and electronic properties because of the spatial separation of electrons and holes caused by the type-II alignment of energy states. Such structure permits access to optical transition energies that are not limited to band gap energies and hence can provide narrow emission spectra and a broad absorption range. In this study, we have investigated the nanostructure size effect on the electronic and optical properties of type II CdSe/ZnTe core shell quantum dot. The carriers wave functions and eigenenergies have been achieved by solving the Schrödinger equation, in the framework of the effective-mass envelope-function theory. The impact of core radius R 1 and the shell radius R 2 on electron and hole energies has been studied for the fundamental and the first excited states. The Coulomb interaction has been calculated and the exciton energy has been deduced. Then, the absorption coefficient has been examined by means of the compact density matrix, the pick of the absorption increases with R 2 and is red shifted. Good excitonic radiative life time in this type II core shell quantum dot has been obtained. The photoluminescence from the CdSe/ZnTe core shell can be adjusted to covers practically all the visible wavelength, which is very important for biomedical and photovoltaics. [ABSTRACT FROM AUTHOR]

Un-doped and Ag-doped CdS quantum dots (QDs) were deposited on spin coated TiO 2 photoanode material by Successive Ionic Layer Adsorption and Reaction (SILAR) method. Systematic investigations were carried out in the deposited un-doped and Ag-doped CdS QDs using powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM) and UV–vis-NIR spectrum. Finally, the FTO/TiO 2 /un-doped CdS and FTO/TiO 2 /Ag-doped CdS QDs were successfully assembled to study the photovoltaic performance under standard one sun illumination of AM 1.5, 100 mW/cm 2 . Photovoltaic parameters, such as short-circuit photocurrent density, open circuit voltage, fill factor and conversion efficiency were found to be 1.37 mA/cm 2 , 0.72 V, 61.5% and 0.61% respectively, for un-doped CdS. Ag-doped CdS QDs shows enhanced photovoltaic parameters such as short-circuit photocurrent density, open circuit voltage, fill factor and conversion efficiency which were 2.35 mA cm 2 , 0.74 V, 71.8% and 1.25% respectively. [ABSTRACT FROM AUTHOR]

We investigated the cellular uptake phenomena of half anti CD3 antibody–CdSe/ZnS quantum dot–conjugate into the live cell by using the confocal laser scanning microscopy. The anti CD3 antibody was efficiently reduced when tris 2–carboxyethyl phosphine hydrochloride was used as a reductant. The molecular weight of obtained half antibody was confirmed by the non–reduction SDS page, and the optimum concentration was 5 mM for obtaining the half antibody. Finally, the confocal laser scanning microscopy image indicates that the CdSe/ZnS quantum dot–conjugate was taken up into the live cell spontaneously by connecting the reduced half antibody around the CdSe/ZnS quantum dot. [ABSTRACT FROM PUBLISHER]

We report here a novel, sensitive detection method for gaseous amines (primary, secondary and tertiary) using thin films of CdSe-based core-shell type quantum dots (CdSe/ZnS and CdSeTe/ZnS) deposited on a glass substrate. The photoluminescence intensity of the quantum dot thin films rapidly decreased on exposure to amine gas in air, and it reversibly recovered after the atmosphere was changed back to air without amine gas. On the other hand, oxygen, nitrogen, argon, carbon dioxide, or hydrogen, all components of natural air, did not affect the photoluminescence intensity of the quantum dot thin films. Interestingly, the photoluminescence of quantum dot films showed higher sensitivity to n -alkylamines, such as hexylamine, when compared with bulky or branched molecules, such as diethylamine and triethylamine. Furthermore, thin films of green-emitting quantum dots showed higher sensitivity to amines when compared with red-emitting ones, which was attributed to the large surface-to-volume ratios of smaller quantum dots. The reversible, reproducible, and selective responses of CdSe-based core-shell type quantum dots to gaseous amines in air suggested that quantum dot thin films could be promising photoluminescence-based optical amine gas sensors. [ABSTRACT FROM AUTHOR]

We have synthesized CdSe (cadmium selenide) quantum dots (QDs) with three different surface-passivating ligands: 3-mercaptopropionic acid (MPA), 4-mercaptobenzoic acid (MBA), and 4-mercaptomethylbenzoic acid (MMBA). Although all the QDs possessed similar diameters and thiol-based ligands, the MPA-passivated QD exhibited the highest photocatalytic H 2 evolution activity in the presence of a polyvinylpyrrolidone-protected Pt (Pt-PVP) colloidal catalyst. Moreover, dynamic light scattering and zeta potential measurements clearly indicated a significant difference in their dispersibility in water. Thus, CdSe-MPA, having the sterically smallest thiol ligand, displayed the largest negative zeta potential and the best dispersibility owing to the presence of negatively charged carboxylate groups on the QD surface. This was sufficient for the QD to disperse as single particles. In contrast, the bulkier MMBA ligand covered the surface of the CdSe QD with a smaller number of ligand moieties, resulting in a smaller zeta potential and the formation of large aggregates (∼126 nm in diameter). In the presence of a Pt-PVP colloid as the hydrogen evolution catalyst, CdSe-MPA formed large aggregates (∼1.6 μm in diameter) with the Pt-PVP colloid by electrostatic interactions. Conversely, CdSe-MMBA did not form such large aggregates with the Pt-PVP colloid. Since the emission of the CdSe QD was effectively quenched in the presence of the Pt-PVP colloid, we concluded that CdSe-MPA exhibits the highest photocatalytic hydrogen evolution activity with the Pt-PVP colloidal catalyst because the electron transfer efficiency from the photosensitizing CdSe QD to the Pt-PVP colloidal catalyst is enhanced by the formation of aggregates. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the effect of the buffer layers on the electronic and optical properties of an exciton (X) and a biexciton (XX) in a type-II CdTe/CdSe quantum dot nanocrystal. In an experimental study, it has been reported that when a CdTe/CdSe quantum dot nanocrystal is coated by a ZnTe material as a buffer layer, the photoluminescence quantum yield is growing from 4 to 20%. We have confirmed theoretically this improvement and extended the calculations to anXXstructure. In the calculations, two different semiconductor materials, CdS and ZnTe, have been considered for the buffer layer. We have theoretically shown that the buffer layer causes an increase in the radiative oscillator strength of bothXandXX. When the ZnTe is used as the buffer layer, the oscillator strength becomes stronger when compared to CdSe buffer material because of higher conduction band offset between CdSe and ZnTe. [ABSTRACT FROM PUBLISHER]

In the study, Al-doped ZnO nanoparticles (Al-ZnO NPs) were prepared by the decomposition of zinc acetate solid solution. The X-ray diffraction results showed that Al 3+ was successfully doped without the formation of Al and Al 2 O 3 impurity phases. The less Al-doping did not change the hexagonal wurtzite crystal structure of ZnO. The ratio of Al to Al + Zn (9.05%) measured by the energy dispersive X-ray also confirmed the formation of Al-ZnO. The Al-ZnO NPs were used as the photoanode material to prepare CdS/CdSe-sensitized solar cell. Compared with the cell based on commercial ZnO NPs (C-ZnO), the short-circuit current density and the fill factor of the cell were increased from 5.8 mA/cm 2 and 34.1% (C-ZnO) to 7.78 mA/cm 2 and 48.7% (Al-ZnO), respectively. The cell efficiency was increased from 1.01% (C-ZnO) to (1.9%) (Al-ZnO) and the increase percentage reached 88.1%. The results of electrochemical impedance spectroscopy and open-circuit voltage-decay suggested the lower carrier transport resistance and the longer electron lifetime of Al-ZnO-based cell. [ABSTRACT FROM AUTHOR]