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Thermal deflection spectroscopy allows to measure very small absorption and uncovers absorption tails extending well below the bulk bandgap energy for CdSe quantum dots films after ligand exchange by sulfide. In this monodispersed system, the redshift, the broadening, and the absorption tails cannot be solely attributed to electronic coupling between the dots. Instead, mixing of hole states from the quantum dot and surface is proposed to dominate the changes of the interband spectra at the absorption edge. [ABSTRACT FROM AUTHOR]

A set of interatomic pair potentials is developed for CdS and ZnS crystals. We show that a simple energy function, which has been used to describe the properties of CdSe [E. Rabani, J. Chem. Phys. 116, 258 (2002)], can be parametrized to accurately describe the lattice and elastic constants, and phonon dispersion relations of bulk CdS and ZnS in the wurtzite and rocksalt crystal structures. The predicted coexistence pressure of the wurtzite and rocksalt structures as well as the equation of state are in good agreement with experimental observations. These new pair potentials enable the study of a wide range of processes in bulk and nanocrystalline II-VI semiconductor materials. [ABSTRACT FROM AUTHOR]

The electronic structures of a CdSe spherical quantum dot in a magnetic field are obtained by using an exact diagonalization method and a variational method within the effective-mass approximation. The dependences of the energies and wave functions of electron states, exciton binding energy, exciton transition energy, and exciton diamagnetic shift on the applied magnetic field are investigated theoretically in detail. It is observed that the degeneracy of magnetic quantum number m is removed due to the Zeeman effect when the magnetic field is present. For the states with m ≥ 0, the electron energies increase as the magnetic field increases. However, for the states with m < 0, the electron energies decrease to a minimum, and then increase with increasing the magnetic field. The energies and wave functions of electron states obtained from the variational method based on the variational functions we proposed are in excellent agreement with the results obtained from the exact diagonalization method we presented. A comparison between the results obtained from the variational functions proposed by us and Xiao is also verified. [ABSTRACT FROM AUTHOR]

Inorganic semiconductor nanoparticles, such as CdSe quantum dots, are considered to be a promising alternative to fullerene derivates for application as electron acceptors in polymer-based bulk heterojunction solar cells. The main potential advantage is the strong light absorption of CdSe nanoparticles with a spectral bandwidth, which can even be tuned, due to the quantum size effect. However, the impact of the particle size on the performance of polymer/CdSe solar cells has remained largely unexplored so far. Therefore, the influence of particle size in hybrid solar cells using a blend of poly(3-hexylthiophene) (P3HT) and quasi-spherical CdSe nanoparticles on relevant cell parameters and the overall solar cell performance is systematically studied in the present work. As the most important result, an increase of the open-circuit voltage (VOC) can be found for smaller nanoparticles and can be explained by an 'effective bandgap' model. In contrast, no significant changes of the short-circuit current density with particle size are observed. Smaller particles were found to yield a lower fill factor, compensating the gain in VOC, so that the power conversion efficiency finally turned out to be independent of the particle size in this study. Spectral differences observed in the respective external quantum efficiency spectra of the solar cells can be attributed to size-dependent changes of the particle absorption. Temperature-dependent measurements of the current-voltage (I-V) characteristics suggest that the transport of photogenerated charge carriers in the bulk heterojunction is limited by localized states, with activation energy beyond thermal energy at room temperature. [ABSTRACT FROM AUTHOR]

We measured the density dependence of both the photoluminescence (PL) spectrum and the PL lifetime of CdSe/ZnS core-shell colloidal quantum dots (QDs) from 0.01 to 10.0 nmol/ml at room temperature. We found that the PL lifetime increased drastically while the PL spectrum changed slightly with an increase in the density of the QDs. The density dependence of the PL lifetime is explained using the imprisonment of resonance radiation model, which has been discussed in atomic systems. [ABSTRACT FROM AUTHOR]

A comprehensive study of the photoluminescence dynamics in newly developed CdSe/ZnS quantum dots with alloyed core/shell interfaces is presented. Time-correlated single photon counting is used to measure the decay of exciton luminescence from both the ensemble and individual quantum dots. For decreasing emission wavelength (i.e., for smaller dots), the ensemble data reveal increasing total decay rates with greater variation. This systematic change is expected for emitters with stronger quantum confinement and more influenced by the surface/interface trap states. In experiments performed on single quantum dots, the photoluminescence trajectories exhibit two-state blinking behavior. The distributions of the 'off'-state probability density are described by an average power-law exponent of 1.5 ± 0.2, while the average decay rate of emission from the threshold-discriminated 'on'-states is estimated to be 0.035 ± 0.004 ns-1. We suggest that in core/shell quantum dots with a large bandgap offset, the compositionally graded energy profile at the interface may not be smooth enough to suppress nonradiative Auger recombination and prevent blinking. [ABSTRACT FROM AUTHOR]

Structural, optical, and photoluminescence investigations of ZnS capped with CdSe films prepared by electron beam evaporation are presented. X-ray diffraction analysis revealed that the ZnS/CdSe nanoparticles films contain cubic cadmium selenide and hexagonal zinc sulfide crystals and the ZnS grain sizes increased with increasing ZnS thickness. The refractive index was evaluated in terms of envelope method, which has been suggested by Swanepoel in the transparent region. The refractive index values were found to increase with increasing ZnS thickness. However, the optical band gap and the extinction coefficient were decreased with increasing ZnS thickness. Photoluminescence (PL) investigations revealed the presence of two broad emission bands. The ZnS thickness significantly influenced the PL intensities. [ABSTRACT FROM AUTHOR]

Bioconjugated CdSe quantum dots are promising reagents for bioimaging applications. Experimentally, the binding of a short peptide has been found to redshift the optical absorption of nanoclusters [J. Tsay et al., J. Phys. Chem. B 109, 1669 (2005)]. This study examines this issue by performing density functional theory (DFT) and time-dependent-DFT calculations to study the ground state and low-lying excited states of (CdSe)6[SCH3]-, a transition metal complex built by binding methanethiolate to a CdSe molecular cluster. Natural bond orbital results show that the redshift is caused by ligand-inorganic cluster orbital interaction. The highest occupied molecular orbital (HOMO) of (CdSe)6 is dominated by selenium 4p orbitals; in contrast, the HOMO of (CdSe)6[SCH3]- is dominated by sulfur 3p orbitals. This difference shows that [SCH3]- binding effectively introduces filled sulfur orbitals above the selenium 4p orbitals of (CdSe)6. The resulting smaller HOMO-LUMO gap of (CdSe)6[SCH3]- indeed leads to redshifts in its excitation energies compared to (CdSe)6. In contrast, binding of multiple NH3 destabilizes cadmium 5p orbitals, which contribute significantly to the lowest unoccupied molecular orbital (LUMO) of (CdSe)6, while leaving the selenium 4p orbitals near the HOMO relatively unaffected. This has the effect of widening the HOMO-LUMO gap of (CdSe)6·6NH3 compared to (CdSe)6. As expected, the excitation energies of the passivated (CdSe)6·6NH3 are also blueshifted compared to (CdSe)6. As far as NH3 is a faithful representation of a surfactant, the results clearly illustrate the differences between the electronic effects of an alkylthiolate versus those of surfactant molecules. Surface passivation of (CdSe)6[SCH3]- is then simulated by coating it with multiple NH3 molecules. The results suggest that the [SCH3]- adsorption induces a redshift in the excitation energies in a surfactant environment. [ABSTRACT FROM AUTHOR]

In this paper, for their use as nanoluminophors on color-conversion white light emitting diodes (LEDs), we present spectrally resolved relative quantum efficiency and relative color (photon) conversion efficiency of CdSe/ZnS core/shell nanocrystal (NC) emitters in the solid-state film. We observe that both the averaged relative quantum efficiency and the averaged relative photon conversion efficiency of these NC solids increase with the increasing photon pump energy. Therefore, the excitation LED platform emitting at shorter wavelengths facilitates such NC luminophor solids to be more efficiently pumped optically. Furthermore, we investigate the spectral time-resolved spectroscopy of NCs in solution and in film with 0.4–2.4 nmol integrated number of NCs in the spectral range of 610–660 nm. We observe that the average lifetime of NCs increases toward longer wavelengths as the number of in-film NCs increases. With the increased amount of NCs, the average lifetime increases even further and the emission of NCs is shifted further toward red. This is attributed to the enhanced nonradiative energy transfer between these NCs due to the inhomogeneous size distribution. Thus, in principle, for fine tuning of the collective color of NCs for color-conversion LEDs, it is important to control the energy transfer by changing the integrated number of NCs. [ABSTRACT FROM AUTHOR]

• The expression of NSE and MAP-2 peaked 5 h after ADSC induced differentiation into neurons. • Neural synapses generated after 5 h of ADSC induction exhibit typical cellular morphology and ultrastructure. • ADSC-derived neurons showing typical endocytic activity driven primarily by the CME pathway. Synapses are essential for facilitating the transmission of information between neurons and for executing neurophysiological processes. Following the exocytosis of neurotransmitters, the synaptic vesicle may quickly undergo endocytosis to preserve the structural integrity of the synapse. When converting adipose-derived stromal cells (ADSCs) into neurons, the ADSCs have already demonstrated comparable morphology, structure, and electrophysiological characteristics to neurons. Nevertheless, there is currently no published study on the endocytotic function of neurons that are produced from ADSCs. This study aimed to examine synaptic endocytosis in neurons derived from ADSCs by qualitatively and quantitatively analyzing the presence of Ap-2, Clathrin, Endophilin, Dynamin, and Hsc70, which are the key proteins involved in clathrin-mediated endocytosis (CME), as well as by using FM1-43 and cadmium selenide quantum dots (CdSe QDs). Additionally, single-cell RNA sequencing (scRNA-seq) was used to look at the levels of both neuronal markers and markers related to CME at the same time. The results of this study provide evidence that synapses in neurons produced from ADSCs have a role in endocytosis, mainly through the CME route. [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) is a promising semiconductor extensively used in manufacturing optoelectronic devices. Compared to the undoped CdSe (Cu 1), the crystallite size of Cu 2 (1 % at. Cu-doped CdSe) increases from 27 to 29 nm , further Cu-doping into CdSe reduced crystallite size to 5 nm. The absorbance behavior exhibited improvement after Cu-doping. Additionally, the reflectance spectrum of Cu 2 displayed enhancement compared to the Cu 1 attributed to increase in crystallite size. The band gap (E g) of undoped CdSe was measured at 1.78 eV, showing an increase to 1.89 eV after Cu-doping. Optical conductivity of CdSe samples exhibited an increase following Cu-doping. Consequently, Cu 2 exhibited optimal characteristics for photodetection among all samples, attributed to its higher crystalline quality, lower lattice strain, reduced defect density, and higher carrier concentration. This study reveals the influence of Cu-doping on CdSe, highlighting essential characteristics to enhance its application in optoelectronics. [ABSTRACT FROM AUTHOR]

Cadmium selenide quantum dots which were synthesized by hydrothermal method was labeled with aptamer, mediated by graphene oxide, a fluorescence aptasensor for the high-sensitive detection of fluoroquinolones was developed. [Display omitted] • CdSe QDs were synthesized and rich in carboxyl groups for further modification. • The advantages of Apt, GO and QDs were combined for highly sensitive FQs detection. • The LOD for FQs in foods sample extracts was 0.42 nM, more sensitive, more specific. • All members of FQs can be specifically recognized to detect the total amount. In view of the urgent need for fluoroquinolones contamination detection in the fields of food safety, a novel aptasensor based on the fluorescence quenching property of graphene oxide (GO) and the fluorescence characteristic of cadmium selenide quantum dots (CdSe QDs) was developed for fluoroquinolones highly sensitive detection in this work. The CdSe QDs with carboxyl-rich surface were synthesized successfully and fluoresced at 525 nm under the optimal excitation light of 366 nm. Based on the hydrophobic and π-π stacking between GO and aptamer, aptamer labeled by CdSe QDs fluorescence (CdSe QDs-apt) were adsorbed by GO and the fluorescence of CdSe QDs was quenched. After the aptamer combined specifically with fluoroquinolones, greater specific force lead to the desorption of CdSe QDs-apt from GO and fluorescence recovery. Represented by Ciprofloxacin (CIP), a member of fluoroquinolones, the fluorescence emission increased with the increasing of CIP concentrations from 8 nM to 500 nM, and the detection limit was 0.42 nM. The spiked recoveries in real samples of honey and milk were 91.5–96.9 % and 90.3–95.2 %, respectively, indicating that the aptasensor was reliable. Moreover, the fluorescence responses of multiple members of fluoroquinolones were found to be consistent, denoting that the fluorescence aptasensor can be used to detect the total amount of multiple members of fluoroquinolones. These results showed that the aptasensor can be used as a promising platform for fluoroquinolones detection. [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) quantum dots (QDs) with different size, 2.5 and 3.2 nm, were successfully deposited on mesoporous titanium dioxide (TiO 2 ) (Degussa-P25) nanostructures by electrophoretic deposition method (EPD) at the applied voltage 100 V for 120 s deposition time. In this study, the morphology of CdSe films deposited by EPD and the performance of the film when assembled into a solar cell were investigated. From the field emission scanning electron microscopy cross-section, the thickness of the CdSe nanoparticles with size 2.5 nm films were 3.4 and 3.0 μ m for CdSe 3.2 nm nanoparticles film. The structure of 2.5 nm is denser than compare of 3.2 nm CdSe nanoparticles. From UV visible spectroscopy, the band gap calculated for 2.5 nm CdSe nanoparticles is 2.28 eV and for 3.2 nm is 2.12 eV. Photovoltaic characterization was performed under an illumination of 100 mW cm -2 . A photovoltaic conversion efficiency of 1.81% was obtained for 2.5 nm CdSe and 2.1% was obtained for 3.2 nm CdSe nanoparticles. This result shows that the photovoltaic efficiency is dependent on CdSe nanoparticle size., (© 2024 IOP Publishing Ltd.)

Green algae are dominant primary producers in aquatic environments. Thus, assessing the influences of pollutants such as nanoparticles on the algae is of high ecological significance. In the current study, cadmium selenide nanoparticles (CdSe NPs) were synthesized using the hydrothermal method and their characteristics were determined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR) techniques. Subsequently, the toxicity of synthesized nanoparticles on the green microalga Chlorella vulgaris was investigated. The observations by SEM confirmed that exposure to CdSe NPs had severe impacts on the algal morphology. Furthermore, the obtained results revealed the toxic effect of CdSe NPs by a decrease in the number of cells. Measurement of antioxidant enzymes activity showed an increase in the activity of catalase, and a decrease in the activity of superoxide dismutase (SOD) at high concentrations of CdSe NPs. The exposure of C. vulgaris to CdSe NPs resulted also in a change in algal pigments as well as total phenol content. Taken together, CdSe NPs appeared to have significant cytotoxic effects on C. vulgaris in the applied concentrations. [ABSTRACT FROM AUTHOR]

An extracellular biosynthesis method has been developed to prepare cadmium selenide (CdSe) quantum dots (QDs) with strong fluorescence emission by incubating cheap Cd and Se inorganic salts with Escherichia coli (E.coli) bacteria. Ultraviolet--visible absorption spectra, photoluminescence (PL) spectra, and high-resolution transmission electron microscopy analysis showed that the biosynthesised CdSe QDs have an average size of 3.1 nm, the excellent optical properties with fluorescence emission around 494 nm, and the good crystallinity. It was found that addition of 80 mg of mercaptosuccinic acid resulted in the formation of CdSe QDs with highest PL intensity. Furthermore, Fourier-transform infrared spectra of assynthesised CdSe QDs confirmed the presence of a surface protein capping layer. The biosynthesised CdSe QDs were incorporated into the yeast cells as illustrated by laser confocal scanning microscopy images, showing a great potential in bio-imaging and bio-labelling application. [ABSTRACT FROM AUTHOR]

Facet‐dependent on‐surface reactions are systematically studied on zinc‐blende CdSe nanoplatelets with atomically‐flat {001} basal facets and small yet non‐polar side facets. The on‐surface half‐reactions between the surface Se sites and Cd carboxylates in the solution are qualitatively equivalent to those on the spheroidal counterparts. Conversely, the on‐surface half‐reactions between the surface Cd sites and the activated Se precursors in solution show a strong facet‐dependence, which includes three distinguishable stages. In the first stage, the Se precursors adsorb onto the small and non‐polar side facets of the nanoplatelets. The second stage is initiated by the adsorbed Se precursors at the side‐basal plane edges and proceeds from the edges to the center of the basal planes in quasi‐zeroth‐order kinetics. In the third stage, the nanoplatelets are dismantled, which includes the creation of a hole in the middle and a build‐up of thick edges. [ABSTRACT FROM AUTHOR]

We report on the growth, grain enhancement, doping, and electron mobility of cadmium selenide (CdSe) thin films deposited using the thermal evaporation method. The optical measurement shows CdSe is a direct bandgap material with an optical bandgap (Egap) of 1.72 eV. CdSe thin films were deposited on fluorine doped tin oxide glass substrates with different thicknesses, and grain size and mobility were measured on the films. CdCl2 was deposited on the films, and the films were subjected to high temperature treatment for several hours. It was found that both grain sizes increased significantly after CdCl2 treatment. The mobility of electrons was measured using the space charge limited current technique, and it was found that the mobility increased significantly after CdCl2 treatment. It was discovered that postdeposition selenization further improved the electrical properties of CdSe thin films by increasing the electron mobility-lifetime product and the photo/dark conductivity ratio. CdSe films after postselenization also showed significantly lower values for midgap states and Urbach energies for valence band tail states. [ABSTRACT FROM AUTHOR]

By color-converting the violet laser diode (VLD) with a cadmium selenide and zinc sulfide (CdSe/ZnS) core-shell-quantum dot (QD) doped polydimethylsiloxane (PDMS) film, the VLD + CdSe/ZnS core-shell-QD transferred white-light with improved color rendering index (CRI) is demonstrated for high-speed indoor visible lighting communication. To facilitate hue saturation value (HSV) of the VLD + CdSe/ZnS core-shell-QD white-lighting module, dual-sized CdSe/ZnS core-shell-QDs with two luminescent wavelengths centered at 515 and 630 nm are doped into the PDMS. The CdSe/ZnS core-shell-QD doped PDMS phosphor with the optimized thickness of 2.5 mm serves as the beam divergent color-converter, which not only excites red (R) and green (G) fluorescence to detune the correlated color temperature (CCT) and CRI of the mixed red/green/violet (RGV) white-light, but also remains the residual VLD signal for data transmission. With a divergent angle of 127°, such a VLD + CdSe/ZnS core-shell-QD can deliver cold white-light with a CCT of 6389 K and a CRI of 63.3 at Commission International de l'Eclairage coordinate of 0.3214, 0.2755. Most important, the residual VLD light component is relatively weak with its wavelength out of the peak optical sensitivity region of the human retina centered at 441 nm. The directly encoded VLD + CdSe/ZnS core-shell-QD white light successfully carries the 16-quadrature amplitude modulation (QAM) discrete multitone data, which supports the maximal transmission data rate of 9.6 Gbit/s with a bit error ratio (BER) of 3.59 × 10−3. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination in water resources has become a potentially serious threat to public health and environment across the globe. In this experiment, we investigated the capacity of titanium dioxide nanoparticles (TiO2 NPs) for selective removal of Cd from wastewater. The TiO2 NPs were prepared using newly developed sol-gel method and sorption attributes were investigated as a function of contact time, sorbent dosage, pH, and initial Cd concentration. Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were successfully employed to delineate the Cd sorption equilibrium results. The Langmuir isotherm and pseudo-second-order kinetic models well fitted the experimental data compared to all other models showing that the Cd sorption was attributed to monolayer sorption and chemisorption process, respectively. The maximum Cd sorption was observed as 89.45% at pH 4.3 with 0.7 g L−1, 30 mg L−1 initial Cd concentration, and 2-h shaking time duration. The SEM analyses revealed that the surface of TiO2 NPs was extremely loaded with the cluster of rough and smooth sites in round form which favored the Cd sorption from solution. Thus, TiO2 NPs could be promising, low cost, and eco-friendly sorbents for Cd adsorption from wastewater. [ABSTRACT FROM AUTHOR]

• CdSe quantum disks, whose photoluminescence peak coincide with the EQE peak of the CIGS solar cells, have been synthesized and embedded into the PMMA to form the LDS layer for CIGS solar cells. • The LDS layer increases the EQE of CIGS devices by up to about 162% in the range 300–460 nm. • The placement of the LDS layer upon the CIGS solar cell improved the electrical power output of the bare cell to 114%. As the luminescent down-shifting (LDS) material, Cadmium selenide (CdSe) quantum disks (QDs) have been synthesized for improving the short-wavelength response of Cu(In, Ga)Se 2 (CIGS) solar cells. The peak of the photoluminescence spectra of the as-prepared QDs is coinciding with the peak of the external quantum efficiency (EQE) of CIGS solar cell. The absorption and photoluminescence spectra of the as-prepared CdSe QDs show that the photons of wavelength below 460 nm, which could not be converted into electricity by CIGS solar cell, would be absorbed by the QDs and generating longer wavelength photons that could contribute to charge carrier generation by the cell. The QDs were embedded into the polymethylmethacrylate (PMMA) forming the colloidal fluorescent mixture. Subsequently, the mixture was applied to the surface of the solar cell as the LDS layer. It is found that the EQE of CIGS devices increases up to about 25% in the range of 300–460 nm due to LDS. The placement of the LDS layer upon the CIGS solar cell improved the electrical power output of the bare cell to 114%. [ABSTRACT FROM AUTHOR]

In the present investigation, the phenomenon of reflection and transmission of plane waves from the interface between fluid half space and transversely isotropic piezothermoelastic solid half space with fractional order derivative is discussed. Energy ratios are computed with the use of amplitude ratios. The law of conservation of energy across the interface is verified. It is found that the energy ratios are the functions of angle of incidence, frequency of independent wave and depend on the different piezothermoelastic material. Cadmium selenide (CdSe) piezothermoelastic material has been considered which is in welded contact with water. Variations of energy ratios corresponding to the reflected and transmitted waves with respect to different values of fractional order derivative are shown graphically. A particular reduced case is also discussed. [ABSTRACT FROM AUTHOR]

CdxSe1-x with(x=0.5) compound have been prepared as alloys successfully. The compound prepared was used to produce films. CdSe films with different thickness (0.5, 1, 1.5, 2)µm by heating evaporation on glass under vacuum (10-5) mbar with rate of deposition equal to 1.5 × 10-3µm/sec. The deposited films on glass are examined at many temperatures (373, 423 and 473)K. XRD type of all cadmium selenide films indicated which these films are hexagonal crystalline and it has direction is (002). The average grain size in this direction is about (35.847)nm; the grain size increases with increasing thicknesses. The optical test founded CdSe films has optical energy gap (Egopt), it reduce from (2.02) to (1.92) eV and from (2.02) to (1.74) eV associated with elevated temperatures of annealing (R.T - 473)K and thickness (0.5- 2)µm, respectively. The dielectric constants, optical constants refractive and extinction coefficient were investigated. [ABSTRACT FROM AUTHOR]

The aim of this paper was cadmium removal from waste water using SiO2 nanoparticles and fungal biomasses. Five treatments were used for cadmium removal. They were inactivated mycelia of Cladosporium sphaerospermum (CLA) and Fusarium oxysporum (FUS), SiO2 nanoparticles (N-Si) and their combinations (N-Si-CLA and N-Si-FUS). The biosorbents natures and combinations were examined by Fourier Transform Infrared (FT-IR) and Scanning Electron Microscope (SEM) where close attachments between combined biosorbents were detected. Different factors affecting cadmium biosorption capacity were tested. It was found that (N-Si-CLA) and (N-Si-FUS) were the most potent biosorbents at pH 7. Thirty minutes contact time exerted maximum sorption capacity. Initial cadmium concentration was optimum at 0.5 mol-1 for highest biosorption capacity. Ca2+ displayed synergistic interfering more than Na+ and K+, respectively. Two real waste water samples collected from two factories were tested to depollute cadmium using the five sorbents. (N-Si-CLA) and (N-Si-FUS) were the most potent adsorbents, where 65.73 % and 54.30% removed in the first sample and 61.33 % and 56.50 % in the second one, respectively. From the results, it was concluded that bioremediation of cadmium from waste water was possible by using SiO2 nanoparticles and fungal biomasses with high efficiency of their combinations. [ABSTRACT FROM AUTHOR]

The structural, lattice dynamical, and electronic properties of non-stoichiometric Cd-Se binary compounds under high pressures were investigated by using a combined approach of particle swarm optimization (PSO) structure search and density functional theory (DFT) calculations. A novel phase of CdSe 4 , which is stable under 50 and 100 GPa, is identified through thermodynamic and lattice kinetic calculations. Unlike the tetrahedrally coordination in wurtzite and zinc-blende CdSe compounds, CdSe 4 possesses stronger anharmonic interactions and is featured by its Cd-centered and Se-centered octahedral building blocks. The central Cd atom adopts equivalent d2sp3 hybridization and forms six equivalent bonds with surround Se atoms. Se atoms not only bond with Cd atoms, but also form bonds with each other. Moreover, band structure and electron localization function analysis reveals that CdSe 4 exhibits metallicity instead of semiconductivity, resulting from its metallic bonding between Se atoms. Our study enriches the II–VI chemistry and provides further understanding to the semiconducting and conducting properties of Cd-Se binary compounds. [ABSTRACT FROM AUTHOR]

Two-dimensional monolayer materials, with thicknesses of up to several atoms, can be obtained from almost every layer-structured material. It is believed that the catalogs of known 2D materials are almost complete, with fewer new graphene-like materials being discovered. Here, we report 2D graphene-like monolayers from monoxides such as BeO, MgO, CaO, SrO, BaO, and rock-salt structured monochlorides such as LiCl, and NaCl using firstprinciple calculations. Two-dimensional materials containing dorbital atoms such as HfO, CdO, and AgCl are predicted. Adopting the same strategy, 2D graphene-like monolayers from mononitrides such as scandium nitride (ScN) and monoselenides such as cadmium selenide (CdSe) are discovered. Stress engineering is found to help stabilize 2D monolayers, through canceling the imaginary frequency of phonon dispersion relation. These 2D monolayers show high dynamic, thermal, kinetic, and mechanic stabilities due to atomic hybridization, and electronic delocalization. [ABSTRACT FROM AUTHOR]

Nanostructured materials can be defined as those materials whose structural elements clusters, crystallites or molecules - have dimensions in the 1-100 nm range. High quality quantum dots have been prepared with advances in the modern colloid chemistry. In the present study we have focused on preparation of CdSe quantum dots (QDs).CdSe prepared via colloidal synthesis in aqueous medium. CdSe QDs optical properties and size were characterized by ultraviolet-visible (UV-vis) absorption spectra, Photoluminescence spectra and DLS measurement. The result showed that the absorption spectra clearly indicate the absorption peak shift from 500 nm to 600 nm on increasing. The particle size average diameter of the CdSe quantum dot is reported as 12.26nm. [ABSTRACT FROM AUTHOR]

This paper reports on the electronic and interfacial properties of a Schottky barrier diode (SBD) prepared from a blend consisting of a matrix semiconductor, poly(9,9-fluorufluorene) (PFB), and a dopant, cadmium selenide (CdSe) quantum dots (QDs) having size less than 5 nm. A uniform blend of PFB and CdSe QDs is prepared in chloroform 1:1 by volume and from a 0.5 wt.% of CdSe QDs and 20 mg/mL of PFB. The Schottky device ITO/PEDOT:PSS/PFB–CdSe/LiF/Ag is fabricated by spin coating the PFB–CdSe QDs blend on a pre-deposited PEDOT:PSS/ITO layer. Lithium fluoride (LiF) and silver (Ag) are thermally deposited via vacuum thermal evaporator as buffer layer and ohmic contact, respectively. The fabricated SBD is studied by current–voltage (I–V) characteristics under dark conditions at 300 K. The device exhibits rectifying behavior with rectification ratio of 301.28 at ± 2.5 V. The interface properties of the device such as series resistance (Rs), barrier height (ϕB), ideality factor (n) and reverse saturation current (I0) are measured to be 58.6 kΩ, 0.99 eV, 1.7 and 2.01 × 10−11 A, respectively. Charge carrier conduction mechanisms across the device such as Richardson–Schottky and Poole–Frenkel effects are studied where Schottky emission was identified at lower voltages while at higher voltages Poole–Frenkel effects were observed. [ABSTRACT FROM AUTHOR]

• CdS/CH 3 NH 3 PbI 3 planar PV devices were synthesized and characterized. • The effects of rapid thermal processing of CH 3 NH 3 PbI 3 and PbI 2 precursor layer on the devices. • RTP resulted higher Voc of 0.62 V and Jsc of 5.2 mA/cm2. • Improvement in crystallinity of the perovskite films due to RTP. • Change in the preferential orientation of perovskite by RTP-PbI 2 as precursor layer. Photovoltaic structures of Glass/FTO/CdS/CH 3 NH 3 PbI 3 have been fabricated and the effects of rapid thermal processing (RTP) on these structures are investigated. First, CdS thin films were deposited by chemical bath deposition on which PbI 2 by spin coating followed by 60 min dipping in 0.1 M CH 3 NH 3 I solution, varying PbI 2 concentrations (0.6–1 M). Studies on the effects of RTP of the CH 3 NH 3 PbI 3 films and the PbI 2 precursor layers revealed an increase in the open-circuit voltage as well as the short curcuit current due to the improved crystallinity and the change in the preferential orientation of the perovskite growth leading to better charge transport. The samples were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, and scanning electron microscopy. The optical and electrical properties were also measured.The perovskite films formed exhibited tetragonal crystalline structure with uniform and compact morphology. The thin films were photoconductive and possessed a direct band gap of 1.5–1.6 eV. The XPS analysis showed the presence of the constituent elements and their chemical states. The photovoltaic parameters of the best cells were: V oc = 0.62 V, J sc = 5.2 mA/cm2, FF = 0.43 and an efficiency of 1.2%. The present work span the scope of the hybrid perovskite mateirals in the conventional p-n heterojuntion solar cells free of any organic HTM layers. [ABSTRACT FROM AUTHOR]

A comprehensive database of the optical response in the form of complex dielectric function (ε) spectra of magnetron co-sputtered CdSe1−xSx alloy thin films is developed spanning the full 0 ≤ x ≤ 1 range of compositions. A parametric model is presented and used to determine ε describing each film while in both as-deposited and thermally annealed states. This model combines a critical point electronic transition lineshape and an Urbach tail in the above- and below-bandgap portions of the measured spectrum, respectively, while maintaining first derivative continuity. Additionally, this hybrid parametric description of ε automatically determines the Urbach energy (EU) describing the width of the sub-bandgap absorption tail, thereby providing a relative measure of the defect density of the modeled material. These as-deposited CdSe1−xSx films are generally found to be the most defective at intermediate compositions with some EU reaching energies > 200 meV. Annealing reduces EU in all films to a relatively uniform value < 100 meV for all compositions. Leveraging the full ε database in modeling CdS-CdSe bi-layer stacks is demonstrated to be effective in detecting the composition gradients resulting from inter-diffusion upon annealing. The accuracy of this technique is verified through excellent agreement with cross sectional energy dispersive X-ray spectroscopy measurements. [ABSTRACT FROM AUTHOR]

Thin CdSe films were produced by electrodeposition at a constant potential onto glass/FTO conducting substrates from sulfuric acid electrolytes (pH 2.2) containing cadmium sulfate, sodium selenite, and addition of sodium lignosulfonates as a surfactant. The films were characterized by X-ray diffraction analysis, Raman spectroscopy, scanning electron microscopy, atomic-force microscopy, spectrophotometry, and photoelectrochemical measurements to examine their structure, composition, surface morphology, and electrical and optical properties. It was found that sodium lignosulfonate improves the electrical properties of the electrodeposited CdSe photoanodes. The operation of a CdSe/FTO/glass photoanode was tested in an electrochemical cell with electrolyte containing the Fe2+/3+ redox pair with various illumination sources. [ABSTRACT FROM AUTHOR]

Nanoparticles of cadmium selenide (CdSe) doped with europium, were synthesized as stabilizing agents using thioglycolic acid ligand. This method is based on the enhancing effect of CdSe quantum dots (QDs) doped with europium on chemiluminescence (CL) emission. This emission was generated by mixing CdSe QDs with manganese (II), iron (II) and chrome (II) sulfates as catalysts in the presence of hydrogen peroxide (H2O2). The structural characteristics and morphology of these nanoparticles were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy, X‐ray pattern and dynamic light scattering methods. The CdSe QDs doped with europium were used as the sensitizer in a luminol−hydrogen peroxide CL system. The sensitized CdSe QDs were analyzed for antibacterial activity against Gram‐positive or Gram‐negative bacteria. The results showed that the CdSe QDs are effective against all the studied bacteria, effectiveness was especially higher for Bacillus subtilis. [ABSTRACT FROM AUTHOR]

The cobalt doped cadmium selenide/biomass carbon spheres (Co-CdSe/BCS) photocatalyst is easily prepared using a transitory hydrothermal reaction lasting 40 min. The Co-CdSe/BCS photocatalyst is constructed using the in situ growth of Co-CdSe nanodots on the surfaces of the BCS. Doped Co2+ generates an electron trap, which can capture the photoinduced electrons, resulting in the efficient separation of the photoinduced electron–hole pairs. Furthermore, the introduction of carbon spheres enhances the optical absorption property and the ability for electron transport. Results of electrochemical characterization and photoluminescence spectra demonstrate that the Co-CdSe/BCS is able to efficiently separate electron–hole pairs and inhibit their recombination. The as-synthesized samples display high efficiency for the photodegradation of methylene blue dye under visible light. This study offers a new strategy to promote photocatalytic performance of the CdSe photocatalyst. [ABSTRACT FROM AUTHOR]

Highlights • Zn 1− x Mg x O:B (BZMO) was prepared by MOCVD method. • Optical and electrical properties of BZMO were investigated. • BZMO was applied as TCO of CIGSSe solar cell, where K-treated CIGSSe is absorber. • 21.1%-efficient CdS-buffer CIGSSe solar cell was fabricated. • 20.2%-efficient Cd-free CIGSSe solar cell was obtained by all-dry process. Abstract Zn 1− x Mg x O:B (BZMO) films were deposited by metal organic chemical vapor deposition (MOCVD). Their optical and electrical properties were investigated for suitability as transparent conductive oxide (TCO) of the Cu(In,Ga)(S,Se) 2 (CIGSSe) solar cells. It is disclosed that with the increase in the [Mg]/([Mg] + [Zn]) of the BZMO up to 0.12 the optical band-gap energy (E g) is increased to 3.52 eV, and the resistivity is reduced to about 3.1 × 10−3 Ω·cm owing to the increase in the Hall mobiltity. Moreover, the severe free-carrier absorption in the BZMO film is not observed. The BZMO is consequently appropriate as the TCO layer of the CIGSSe solar cells. The K-treated CIGSSe layers were applied as the absorbers of the solar cells. As a result, the 21.1%-efficient CIGSSe solar cell with a structure of Zn 0.88 Mg 0.12 O:B/CdS/CIGSSe/Mo/glass is obtained. In addition, the 20.2%-efficient Cd-free CIGSSe solar with a structure of Zn 0.88 Mg 0.12 O:B/Zn 0.80 Mg 0.20 O/CIGSSe/Mo/glass, fabricated by all-dry process, is realized with high short-circuit current density (J SC) of 39.7 mA/cm2. The high J SC is attributable to no optical loss in CdS buffer layer, no severe free carrier absorption, and the increased E g of the BZMO layer. [ABSTRACT FROM AUTHOR]

In this study, I–V and C–V characteristics of the Al/(CdSe-PVA)/p-Si/Al (MPS) structure have been investigated the by taking into account double-exponential I–V and NC behavior. The structural characterization of CdSe nanocrystals were analyzed by X-ray diffraction (XRD), scanning electron micros-copy (SEM), and energy dispersive X-ray (EDX) techniques. These results show that the prepared CdSe consists of spherical monodispersed nanocrystalites of about 200 nm; aggregated in the form of poly-dispersive nanoclusters of arbitrary shape with the size in the range of 150-300 nm and they are in good agreement with those estimated from the XRD pattern. The forward bias LnI–V plot of the MPS structure has two linear parts which are called low bias Region 1 (R1:0.25-0.65 V) and moderate bias Region 2 (R2:0.70-1.20 V). The ideality factor (n) and barrier height (BH:ΦB0) were found to be 9.38 and 0.61 eV for R1 and 6.51 and 0.65 eV for R2, respectively. The current conduction/transport mechanism (CCM/CTM) are also defined by forward I–VLn(I)–V and reverse bias In(IR)–VR1/2 plots. I–VLn(I)–V plot has also two linear parts which are also called (R1:-3.02/-0.29) and (R2:-0.10/1.60) obey I ~ Vm law. The slope (m) of them was found to be 1.63 and 4.57 which are corresponding to ohmic and trap-charge limited current (TCLC) mechanisms, respectively. Moreover, the value of ΦB(C–V) was found from the linear part of C−2-V plot as 0.79 eV which is higher than the obtained forward bias lnI–V plot due to the nature of measured method. [ABSTRACT FROM AUTHOR]

In this paper, the photocatalytic behavior of CdSe/CdS quantum dots (QDs) in reducing the graphene oxide (GO) with different surface ligands was investigated. Here, three surface ligands of different functional groups (oleic acid, poly (acrylic acid polymers) and S2−) were selected to study the influence of surface ligands on photocatalytic behavior of the CdSe/CdS QDs. Meanwhile, the obtained samples can be used as photocatalyst, and the photocatalytic activity was evaluated by photodegrading a methylene blue solution. It turned out that the QDs–S2−–GO sample showed the highest photocatalytic activity under visible-light irradiation. Different surface ligand has different influence on the charge separation efficiency, which has different influence on photocatalytic behavior. The results show that the photocatalytic behavior is highly dependent on the electron attracting ability of the surface ligands on the CdSe/CdS QDs. Finally, a possible photocatalytic mechanism is proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hollow MoSe 2 /CdSe nanospheres were prepared by one-pot solvothermal strategy. • It is first time to synthesize hollow MoSe 2 nanostructure without templates. • Both experimental and DFT calculations reveal the Z-scheme mechanism. • Full spectrum harvest, hollow structure and charge separation induce remarkable activity. • The Langmuir adsorption, low pH and thermal effect benefits to photocatalysis. Abstract For better use of solar energy, the development of full-spectrum photocatalysts has attracted most attentions. In this research, uniform hollow MoSe 2 /CdSe nanospheres (250 nm) were prepared by one-pot solvothermal strategy. It is the first time to synthesize hollow MoSe 2 based nanostructure without any template/surfactant assistance. By varying reaction time, the formation mechanism was investigated, illuminating that the novel hollow structure is derived from the Kirkendall Effect. Both experimental and density functional theory (DFT) calculations reveal the Z-scheme mechanism of the charge transfer in the heterostructure. The hollow MoSe 2 /CdSe nanospheres (MC2) possess the remarkable photocatalytic activity in degradation of Cr(VI) (125 mg g−1, simulated sunlight), owing to the high harvest of full spectrum, porous hollow structure and effective charge separation/transfer. Furthermore, the photocatalytic process was further studied in detail, showing that the Langmuir single-layer adsorption behavior, low pH value condition, and thermal effect also benefit to the high photoreduction performance. Benefiting from the Z-scheme mechanism, the high redox activity make sure the water splitting capacity of MC2 (7120.0 and 348.0 μmol h−1 g−1 of H 2 and O 2 evolution) under simulated sunlight irradiation and its AQY for H 2 evolution at 670 nm reaches up to 27.2% (50 mg MC2). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Modifying TiO 2 films with 4-mercaptobenzoic acid (MBA) as linkers. • Adjusting modification time of MBA on the surface of TiO 2 films. • Resolving aggregation of QDs on films. • Higher loading amount and slower electron-hole recombination. • The best device with 3 min of MBA modification exhibits an efficiency of 5.58%. Abstract Recently, the pre-synthesized oil-soluble quantum dots (QDs) have triggered great interests due to advantages of monodispersity, stability and easy synthesis. Aggregation of QDs is the reason for low loading and poor efficiency during the in situ ligand exchange linker-assisted assembly process of preparing photovoltaic devices. In this work, we modify TiO 2 films with 4-mercaptobenzoic acid (MBA) as linkers and adjust modification time (MT) of MBA on the surface of TiO 2 films. As the MT increases from 0 to 6 min, even 360 min, loading amount of QDs and photovoltaic performance improve first and then decrease. The results of line scan in cross-sectional view of photoanodes show that QDs uniformly distribute throughout the short-MT films thickness, while obvious aggregation occur in the surface of long-MT films. The best device with 3 min of MBA modification exhibits an optimal efficiency of 5.58%. [ABSTRACT FROM AUTHOR]