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Erbium-doped cadmium selenide thin films grown on 7059 Corning glass by means of a chemical bath at 80 °C were prepared. Doping was performed by adding an aqueous Er(NO3)33·H2O dilution to the CdSe growth solution. The volume of Er doping solution was varied to obtain different Er concentration (x at%). Thus, in the Cd1−xErxSe samples, the x values obtained were in the 0.0–7.8 at% interval. The set of the CdSe:Er thin films synthesized in the hexagonal wurtzite (WZ) crystalline phase are characterized by lattice parameters (a and c) that increase until x = 2.4% and that subsequently decrease as the concentration of x increases. Therefore, in the primitive unit cell volume (UC), the same effect was observed. Physical parameters such as nanocrystal size, direct band gap (Eg), and optical longitudinal vibrational phonon on the other hand, shift in an opposite way to that of UC as a function of x. All the samples exhibit photoluminescence (PL) emission which consists of a single broad band in the 1.3 ≤ hν ≤ 2.5 eV range (954 ≥ λ ≥ 496 nm), where the maximum of the PL-band shift depends on x in the same way as the former parameters. The PL band intensity shows a singular behavior since it increases as x augments but exhibits a strong decreasing trend in the intermediate region of the x range. Dark d.c. conductivity experiences a high increase with the lower x value, however, it gradually decreases as x increases, which suggests that the Er3+ ions are not only located in Cd2+ sites, but also in interstitial sites and at the surface. Different physical properties are correlated among them and discussed considering information from similar reports in the literature. [ABSTRACT FROM AUTHOR]

The effect of the type of doping (surface (I) or bulk (II) doping) on the character of the dipole plasmon mode in semiconductor CdSe nanocrystals has been studied. It was found that in case I (donors located on the surface of the nanocrystal) the collective mode had a rotational character and only the angular degrees of freedom were excited. On the contrary, in case II the charge of the dopant impurities was distributed throughout the system and plasmon excitation was the oscillation of delocalized charge carriers in the direction normal to the surface. It was shown that the position of the resonance line was determined not only by the concentration of free charges, but also by the character of their collective motion determining by the type of doping.

This study elucidates the propagation of surface (Rayleigh type) waves in a homogeneous, transversely isotropic, piezothermoelastic half-space subjected to stress free, electrically open or shorted, and thermally insulated or isothermal boundary conditions, based on GN-III type and three-phase-lag thermoelastic models. Plane harmonic wave solutions are employed to find the mechanical displacements, electrical potential, and temperature change. With the aid of these expressions, stresses, electrical displacement, and temperature gradient are derived. Based on different boundary conditions, four secular equations are derived in the considered half-space. Path of the surface particles traces an elliptic path in vertical plane parallel to the direction of wave propagation and the eccentricity of the ellipse is calculated. Particle path degenerates a straight line when there is no phase difference between vertical and horizontal components of displacements. A pre-established analysis is discussed as a particular case of this study. Effect of various characteristics of waves like phase velocity, attenuation coefficient, and specific loss is demonstrated graphically for the GN-III type and three-phase-lag thermoelastic models engaging cadmium selenide (6 mm class) material of hexagonal symmetry. This mathematical framework may be utilized to design and develop temperature sensors, and other piezoelectric surface acoustic wave (SAW) devices. [ABSTRACT FROM AUTHOR]

Fabrication and characterization of hybrid nanomats containing quantum dots can play a prominent role in the development of advanced biosensors and bio-based semiconductors. Owing to their size-dependent properties and controlled nanostructures, quantum dots (QDs) exhibit distinct optical and electronic characteristics. However, QDs include heavy metals and often require stabilizing agents which are toxic for biological applications. Here, to mitigate the use of toxic ligands, cadmium selenide quantum dots (CdSe QDs) were synthesized in situ with polyvinylpyrrolidone (PVP) at room temperature. The addition of PVP polymer provided size regulation, stability, and control over size distribution of CdSe QDs. The characterization of the optical properties of the CdSe QDs was performed using fluorescence and ultraviolet–visible (UV-Vis) spectroscopy. CdSe QDs exhibited a typical absorbance peak at 280 nm and a photoluminescence emission peak at 580 nm. Transmission electron microscopy (TEM) micrographs demonstrated that CdSe QDs having an average size of 6 ± 4 nm were obtained via wet chemistry method. CdSe QDs were immobilized in a blend of PVP and poly(L-lactide-co-ε-caprolactone) (PL-b-CL) copolymer that was electrospun to produce nanofibers. Scanning electron microscopy (SEM), thermal analyses and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) were used to characterize properties of fabricated nanofibers. Both pristine and hybrid nanofibers possessed cylindrical geometry and rough surface features, facilitating increased surface area. Infrared absorption spectra showed a slight shift in absorbance peaks due to interaction of PVP-coated CdSe QDs and nanofiber matrix. The presence of CdSe QDs influenced the fiber diameter and their thermal stability. Further, in vitro biological analyses of hybrid nanofibers showed promising antibacterial effect and decline in cancer cell viability. This study offers a simple approach to obtain hybrid nanomats immobilized with size-controlled PVP-coated CdSe QDs, which have potential applications as biosensors and antibacterial and anticancer cell agents. [ABSTRACT FROM AUTHOR]

Dyes are employed in industrial processes that result in large volumes of wastewater. This situation is hazardous for the environment and human health and requires the development of cost effective, environmentally friendly, and sustainable technologies. Photocatalysis with polymer supported quantum dots is promising for the treatment of dye containing wastewater. Here, polybutylene adipate terephthalate (PBAT) cadmium selenide quantum dots (CdSe QDs) composites were produced by solution casting for methylene blue (MB) removal from wastewater. The characterization of PBAT/CdSe QDs nanocomposite films was performed by x-ray diffraction, Fourier transform infrared spectroscopy, and spectrophotometry. The influence of pH, initial MB concentration, PBAT/QDs composition, and catalyst dosage upon the efficiency of photocatalytic degradation were investigated. The highest efficiency was obtained using 0.8 g/L catalyst dosage at pH 12.0 with a value of 98.27% in 120 min. This study shows that biodegradable PBAT and CdSe QDs are suitable for photocatalysis-based wastewater treatment. [ABSTRACT FROM AUTHOR]

Quantum dots are tiny semiconductor nanocrystals. Their dimensions are between about 2 and 10 nm. They have attracted much attention due to their unique electronic and optical properties. These particles can be synthesized in a variety of ways. Synthesis methods of quantum dots can be classified into top-down and bottom-up. Top-down approach is a fragmentation process of bulk material. In contrast to top-down, quantum dots are constructed from atoms and molecules of the material at bottom-up procedure. Ball milling, optical lithography, laser ablation and arc-discharge are some top-down methods. However, chemical reduction, thermal decomposition, sol-gel and ultrasonic spray pyrolysis are bottom-up methods. In this study, chemical hot-injection synthesis method of cadmium selenide quantum dots which is a kind of bottom-up procedure will be explained. Cadmium selenide quantum dots have been grown in hot solvent at 259°C. Concentration of cadmium selenide quantum dots dispersed in toluene has been adjusted by observing their first exciton peak. First excitonic absorbance peak of cadmium selenide quantum dots has been measured at around 2.18 eV. Transmission electron microscope photo of these growth quantum dots has been shown. The average diameter of cadmium selenide quantum dots has been found to be approximately 3.48 nm. Lattice fringe spacing of cadmium selenide quantum dots has been measured as ~0.35 nm. [ABSTRACT FROM AUTHOR]

Thin Films of different thickness of Cadmium Selenide (CdSe) were prepared by using thermal evaporation technique on a glass substrate, and investigation of dielectric properties as a function of frequency in the range up to 1 MHZ using Auto Lab Potentiostat/Galvanostat meter was conducted. Preliminary data for complex parameters i.e. complex dielectric constant (ε*), complex impedance (Z*), electric modulus (M*), tangent loss (δ) and conductivity (σ) has been calculated. All these properties are used to explore various processes that contribute to the dielectric spectroscopy investigation. [ABSTRACT FROM AUTHOR]

Photoelectronic properties of nanocrystalline CdSethin films prepared by chemical bath deposition (CBD) technique at room temperature are studied taking its molar concentration as a function. Structural analysis of the deposited thin films shows that change of molarity brings a variation in the crystalline sizes of the thin films. Such thin films show suitable photoelectronic properties for the construction of different optoelectronic devices. The photocurrents are observed to be significantly defect controlled in the visible range of wavelengths. The transport mechanism for the thin films is generally a doubly activated process and the photocurrent decay characteristics curves are found to exhibit 2 different decay times which actually correspond to 2 distinct trap levels. [ABSTRACT FROM AUTHOR]

The optical properties of a cadmium selenide (CdSe) film doped with aluminum (Al) at a rate of (3%) have been studied. It was deposited on glass substrates at 250 K with a thickness of 0.15 µm and a deposition rate of 2± 0.1 m.sec-1 using a thermal evaporation technique to create the compound. The optical characteristics of the produced film were investigated after being subjected to irradiation by 50 mW, 1064 nm IR laser for 15 minutes at a distance of 0.5 m. Through monitoring the absorbance and transmission spectra of prepared thin film across the wavelength range (190-1100 nm), the optical energy gap value for the permitted direct electronic transitions was determined, and the absorption and reflectivity coefficients were computed and investigated. The optical experiments included computing the optical constants, and result explained that the optical energy gap decreased from (1.76 eV) to (1.64 eV) following irradiation (extinction coefficient, refractive index, and absorption coefficient). [ABSTRACT FROM AUTHOR]

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A sincere effort has been taken to design and fabricate a Cadmium Selenide (CdSe) Quantum Dot solar cell by varying the concentration of Se (0.1, 0.2, and 0.3 mmol) using ethanol and ethylenediamine as solvents in equal ratio. The proposed solar cell is tested for photoconversion efficiency with different sizes of the quantum dots (7 nm, 8 nm, and 8.9 nm). The XRD pattern reveals that CdSe quantum dots has attained cubic structure with face-centered lattice. The prepared quantum dots are subjected to UV–Visible spectroscopic study and bandgaps are obtained as 3.02 eV, 2.91 eV, and 2.89 eV for 7 nm, 8 nm, and 8.9 nm quantum dots, respectively. In the photoluminescence spectroscopy, two emission peaks are observed at 370 nm and at 473 nm which corresponds to the band–to–band transition. Among the different sizes of the quantum dots, the particle size of 7 nm has given higher photoconversion efficiency of 0.6680% with 0.1 mmol of Se in CdSe. [ABSTRACT FROM AUTHOR]

This study investigated the use of inorganic cadmium selenide nanoplatelets (CdSe NPLs) to enhance the performance of X-ray detectors. The active layer of the detector comprised a bulk heterojunction composed of PCDTBT:PC 71 BM: CdSe NPLs with three different aspect ratios (ARs = 3:1, 1:1, and 6:1). The CdSe NPLs, synthesized with a thickness of five monolayers, were controlled by adjusting the molar mass ratios of Cd(OAc) 2 and Cd(OAc) 2 ∙2 H 2 O. Each detector was characterized by analyzing its series resistance, collection irradiation, dark current density, detection sensitivity, charge mobility, and defect density via the collected charges. The detector containing CdSe NPLs with an aspect ratio of 1:1 demonstrated the most favorable performance, exhibiting improved carrier generation and transport properties, resulting in a 23.36 % increase in sensitivity compared with the detector without CdSe NPLs. Through experimentation, the optimal content of CdSe NPLs in the active layer was determined to be 1 wt%, yielding the highest sensitivity of 3.96 × 103 μC∙Gy−1∙cm−2. This study underscores the potential of CdSe NPLs as promising materials for X-ray detector applications. • Utilized CdSe nanoplatelets (NPLs) to enhance X-ray detector performance. • Demonstrated 23.36 % sensitivity increase with optimized CdSe NPLs (AR = 1:1). • Revealed CdSe NPLs altered surface morphology, enhancing light absorption. • Highlighted potential of CdSe NPLs for improving various optoelectronic devices. [ABSTRACT FROM AUTHOR]

Improving the practical uses of a multifunctional humidity sensor requires developing an easy, economical, and environmentally friendly synthesis process. Unfortunately, most humidity sensors have a complicated fabrication process, which drives up their price and restricts their range of applications. In this present work, quantum dots have prevailed as a potential sensing material owing to their small size and large surface area. Herein, we reported the three different colored (green, yellow, and red) based cadmium selenide (CdSe) quantum dots (QDs) using a solution-processed method. Physical characterization of as synthesized CdSe QDs is confirmed using photoluminescence (PL), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–visible analysis, diffused light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR). TEM analysis of CdSe QDs revealed the average particle size of 6 nm. These CdSe QDs were further employed as capacitive humidity sensors. Among the investigated samples, Cd-1 (prepared by 225℃) exhibited the highest sensitivity 93.842 pF/% RH with a rapid response and recovery time of 10 s and 13 s, respectively at 20 Hz. The excellent sensitivity of the Cd-1 is accredited to its least particle size and wider energy band gap as compared to Cd-2 and Cd-3 (prepared by 235 and 245℃) samples. Overall, this work opens an avenue for high performance CdSe QDs based humidity sensors. [Display omitted] • A facile synthesis of CdSe quantum dots at different temperatures. • The humidity sensing characteristics, first time investigated without any surface modification. • Synthesized CdSe quantum dots showed size at 2–10 nm. • CdSe (Cd-1) at 225℃ exhibited the highest sensitivity 93.842 pF/% RH. • A rapid response and recovery time of 10 s and 13 s, respectively at 20 Hz. [ABSTRACT FROM AUTHOR]

Nanostructured cadmium sulpho selenide (CdSSe) films have been grown onto glass substrates for different deposition durations via a facile solution-based method known as chemical bath deposition (CBD). XRD studies revealed that the crystallites in the films possessed hexagonal (wurtzite) structures with predominant orientation along the (002) plane. The crystallite size increased from ∼5.95 nm to ∼16.69 nm with the increase in deposition duration from 1 h to 4 h. The absorbance, transmittance and reflectance measurements were carried out. A transparency of ∼(50–80) % was obtained for the films. The direct optical energy band gap was found to decrease from 1.982 eV to 1.952 eV with the increment of deposition duration from 1 h to 4 h. SEM micrographs of the films revealed the presence of nano spherical-shaped grains with an average size ranging from ∼305 nm to ∼612 nm. HRTEM images illustrated the presence of compact nano-spherical grains and nano-crystallites distributed in random orientations. Raman spectroscopy divulged the presence of CdSe and CdS vibrational Raman modes and overtones in the films. PL spectra revealed a prominent red emission band along with weak luminescent bands in the yellow-red emission region. The presence of Cd–Se and Cd–S bonds in the films was validated using FTIR analysis. Electrical investigation revealed the linear current‒voltage relationship for the films with the rise in conductivity with deposition duration. Hence, deposition duration stands out as a vital parameter for modulating the properties of CdSSe thin films for use in photovoltaic devices and optoelectronics. [Display omitted] • CdSSe thin films have been grown using CBD method at different deposition duration. • XRD analysis reveals the nanocrystalline nature of the thin films. • SEM images confirmed the presence of nano spherical-shaped grains in the films. • TEM images confirmed the formation of nanocrystallites in the films. • Deposition duration of 4 h was found to be optimal for the growth of uniform and compact CdSSe thin films. [ABSTRACT FROM AUTHOR]

This work sheds light on the potential of Cadmium Selenide (CdSe) solar cells for indoor applications. CdSe boasts a wide direct bandgap, high carrier mobility, and a high absorption coefficient, making it an attractive candidate for harnessing ambient indoor light. Our study centers around an experimental solar cell architecture composed of FTO/CdSe/PEDOT:PSS/CuI/ITO, which exhibits a power conversion efficiency (PCE) of 6.00 %. Through a meticulous analysis of the core technological aspects of this cell, we successfully replicate the measured current-voltage characteristics and other experimental data, affirming the validity of our simulation modeling approach. Moving forward, we delve into the design and optimization of CdSe-based solar cells under white LED illumination. We emphasize the pivotal role of a double-hole transport layer (HTL) configuration over a single HTL, with a focus on optimizing the alignment between the HTL/back contact and HTL/absorber interfaces. The strategic incorporation of a heavily doped p-type HTL material, boasting both a deep valence band maximum (VBM) and a shallow conduction band minimum (CBM), is identified as paramount, especially for a deep VBM absorber like CdSe. Adding double HTL materials also facilitates efficient hole collection within the CdSe thin film while mitigating undesirable electron-hole recombination at the critical interface between the hole collection layer and the electrode. The implementation of a double HTL configuration based on CuI/ZnTe:Cu or CuI/BCS significantly enhances performance, resulting in a PCE in the order of 20 % under 200 lux and 2900 K LED illumination. Moreover, we introduce the single HTL design to provide other alternatives for efficiency boosting. Upon increasing the work function of the front contact, it is found that the valence band offset between the HTL and the absorber can be engineered, resulting in a PCE above 21.5 %. • The CdSe-based solar cell is a potential solution for indoor light harvesting due to their wide bandgap. • A calibration step of the simulation model against fabricated CdSe cell enables accurate validation of the simulation model. • The design is based on a double HTL structure based on CuI/ZnTe:Cu or CuI/BCS to enhance band alignment. • A PCE in the order of 20 % under 200 lux and 2900 K LED illumination was achieved. • Based on a single HTL and engineered front contact design, a PCE above 21.5 % is achieved. [ABSTRACT FROM AUTHOR]

The use of microfluidics in chemical synthesis is topical due to the potential to improve reproducibility and the ability promptly interrogate a wide range of reaction parameters, the latter of which is necessary for the training of artificial intelligence (AI) algorithms. Applying microfluidic techniques to semiconductor nanocrystals, or quantum dots (QDs), is challenging due to the need for a high-temperature nucleation event followed by particle growth at lower temperatures. Such a high-temperature gradient can be realized using complex, segmented microfluidic reactor designs, which represents an engineering approach. Here, an alternative chemical approach is demonstrated using the cluster seed method of nanoparticle synthesis in a simple microfluidic reactor system. This enables quantum dot nucleation at lower temperatures due to the presence of molecular organometallic compounds (NMe4)4[Cd10Se4(SPh)16] and (NMe4)4[Zn10Se4(SPh)16]. This integration of cluster seeding with microfluidics affords a new mechanism to tailor the reaction conditions for optimizing yields and tuning product properties.

We present the first experimental optical absorption spectra of isolated CdSe 2 + and Cd2 Se 2 + species in the photon energy range ℏω = 1.9–4.9 eV. We probe the optical response by measuring photodissociation cross sections and combine our results with time-dependent density functional theory and equation-of-motion coupled cluster calculations. Structural candidates for the time-dependent excited state calculations are generated by a density functional theory based genetic algorithm as a global geometry optimization tool. This approach allows us to determine the cluster geometries present in our molecular beams by a comparison of experimental spectra with theoretical predictions for putative global minimum candidates. For CdSe 2 + , an excellent agreement between the global minimum and the experimental results is presented. We identify the global minimum geometry of Cd2 Se 2 + as a trapezium, which is built up of a neutral Se2 and a cationic Cd 2 + unit, in contrast to what was previously proposed. We find an excellent overall agreement between experimental spectra and excited state calculations. We further study the influence of total and partial charges on the optical and geometric properties of Cd2Se2 and compare our findings to CdSe quantum dots and to bulk CdSe. [ABSTRACT FROM AUTHOR]

Two-Dimensional Electronic Spectroscopy (2DES) is performed on CdSe colloidal quantum dots. These experiments reveal new observations on exciton structure and dynamics in quantum dots, expanding upon prior transient absorption measurements of excitonics in these systems. The 2DES method enables the separation of line broadening mechanisms, thereby better revealing the excitonic lineshapes and biexcitonic interactions. 2DES enables more information rich spectral probing of coherent phonons and their coupling to excitons. The data show spectral modulations and drifts, with differences based upon whether one monitors the excitation energy (E1) or emission energy (E3). These measurements reveal both homogeneous and inhomogeneous broadenings, as well as static and dynamic line broadening. The longitudinal optical phonon modulates the dynamic absorption spectrum both in energy and linewidth. These experiments enable measurement of hot exciton cooling with improved resolution in energy and time. These 2DES results are consistent with prior excitonic state-resolved transient absorption measurements, albeit with the addition of contributions due to coherent phonons. Finally these 2DES experiments enable disentangling of coupling versus relaxation contributions to the signals, further offering a test of electronic structure theory. [ABSTRACT FROM AUTHOR]

Today, the rapid change that occurs with the acceleration of research and studies in thin film materials creates new opportunities for the development of new processes, materials, and technologies. In this study, cadmium selenide (CdSe) thin films were deposited on the glass substrate by successive ionic layer adsorption and reaction (SILAR) method with 30, 40, and 50 deposition cycles. Structural, optical, electrical, and gas sensing properties of CdSe thin films were investigated as a function of the deposition cycle directly related to the thickness of samples. The transmission decreased from 13 to 5% from 30 to 50 cycles whereas increasing in absorbance from 0.6 to 1.2. Optical bandgap values were calculated as 1.83, 1.79, and 1.76 eV for 30 cycle, 40 cycle, and 50 cycle, respectively. From Raman analyses, CdSe thin films have two strong modes at 200 cm−1 for all films and 819, 838, and 872 cm−1 for 50CdSe, 40CdSe, and 30CdSe, respectively. CO2 gas detection measurements from 10 to 50 ppm were made for all samples at room temperature. The responses of 10 ppm CO2 gas sensing were calculated as 4%, 5%, and 7% for 30 cycle, 40 cycle, and 50 cycle at room temperature. It was seen that the best results were obtained with the 50 cycle thin film. The effect of deposition cycle was investigated on the structural, morphological, optical, and electrical properties of the films in detail. [ABSTRACT FROM AUTHOR]

There are tremendous efforts to realize the idea of employing photoelectrochemical (PEC) technology for generating chemical energy from solar energy. The most important feature of this technology is to coordinate the energetics of an electrochemical reaction with the solar spectrum. So, the photoelectrochemistry of a semiconducting material plays a vital role in this arena. Exploring an efficient and stable semiconductor material for such purpose is an essential prospect. There are several sulfide selenide‐based semiconductors viz. II‐VI (Zn/Cd = S/Se) semiconductors those exhibit high potential in PEC application. Nonetheless, they suffer by certain corrosion issues, which are important to be reviewed and are discussed here. This review highlights the significant role of cadmium chalcogenides among various materials explored in this technology. CdS is the most studied system among all those with perfect band gap and band‐edge position exhibiting material, desired for photoanode in PEC cell. Next, recent progresses achieving enhancement in the performance of CdS photoanodes by doping, modifying the surface, morphology reconstruction, and engraving heterostructure is discussed in detail. The role of the nanostructured techniques, improved photo electrochemistry with redox couples, and advanced interfacial and band gap engineering is explored to overcome the lack of chemical stability of CdS. The review concludes with the bright scope of CdS as an efficient PEC material in the form of combined semiconductor systems with an optimum band gap, bandedge, and their complimentary properties rather than a single component material. [ABSTRACT FROM AUTHOR]

Photodegradable films of low-density polyethylene (LDPE) were prepared by melt blending of the polymer with cadmium selenide (CdSe) and trisilver phosphate (Ag3PO4) as photo-catalysts and manganese stearate as pro-oxidant. The samples were irradiated with visible and ultra-violet light. Scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and viscometry measurements were used to investigate the microstructure of the films. The results showed that the combination of the photo-catalysts and the pro-oxidants has synergistic effect on the photo-degradation of the LDPE and accelerates a lot more its degradation process than when only the pro-oxidant was used. [ABSTRACT FROM AUTHOR]

Doping is a simple method to modulate the electronic configuration of semiconductor photocatalysts. This study regulated the energy band structure of CdSe nanosheets by Ag doping, which reduced the energy bandwidth of CdSe nanosheets by increasing the carrier density, thereby improving the efficiency of the photocatalytic reduction of uranium by CdSe nanosheets. A 96% removal of U-(VI) was achieved by 3% Ag-CdSe nanosheets, which was 1.9 and 1.2 times higher than that of pristine CdSe nanosheets (50%), and 1% Ag-CdSe nanosheets (81%), respectively. Additionally, at pH = 4.0 and a solid–liquid ratio of 0.25, the reduction of uranium by 3% Ag-CdSe nanosheets (765 mg/g) was 2.2 times higher than that of pristine CdSe nanosheets (345.6 mg/g). This study provides a new idea for other efficient photocatalysts designed for uranium reduction. [ABSTRACT FROM AUTHOR]

II–VI nanocrystalline semiconductors offer a wide range of applications in electronics, optoelectronics, and photonics. The study of the morphological, electrical, and optical properties of Cadmium selenide (CdSe) nanoparticles prepared with tri ethanolamine (TEA) as a complex agent is reported in the paper. Cadmium acetate as a Cd source and (Na2SeO3) as a Se precursor. Transmission electron microscope (TEM), field emission scanning electron microscope (FESEM), energy dispersive x-ray (EDX), and ultraviolet-visible spectroscopy (UV-VIS) were used to characterise the synthesised nanoparticles for their optical, compositional, morphological, and electrical properties. The film of CdSe was deposited on the glass substrate. The electrical characterisation of CdSe thin films at various temperatures dark electrical conductivity and photoconductivity reveal that the films were semiconducting in nature, indicating the suitability of these films for photo sensor applications. [ABSTRACT FROM AUTHOR]

Monolayer (ML) transition metal dichalcogenides (TMDCs) are suitable for use in low‐threshold, room‐temperature lasers. 2D semiconductor lasers are coherent, compact, and are suitable for multispectral light sources. 0D quantum dot technology has been applied in broadband‐emitting devices and high‐quality display systems. Herein, dual‐color continuous‐wave microcavity lasers are investigated by integrating a tungsten diselenide (WSe2) monolayer and cadmium selenide (CdSe) quantum dots (QDs) into a single microdisk cavity. The hybrid TMDC/QD microcavity device not only achieves lasing in two distinct wavelength regions but also boosts the lasing performances of the WSe2 monolayer due to the energy conversion between the two gain materials. Variations in the spectra obtained under power‐dependent lasing are examined, and the temporal coherence properties of the lasing signals are also characterized to verify the lasing actions. The results indicate that the lasing threshold of the 2D WSe2 monolayer cavity with the CdSe QDs is reduced by more than 2.5 times compared with the WSe2 cavity without the QDs. These findings both expand the wavelength range of TMDC‐based compact lasers at room temperature and facilitate their implementation in applications such as photonic integrated circuits, broadband light‐emitting diodes, and quantum display systems. [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]

Surface passivation of colloidal semiconductor nanocrystals is usually performed at elevated temperatures with undefined changes to core nanocrystals. Using a prenucleation-stage sample of ZnSe-containing clusters (prepared at 160 °C), the first surface passivation is reported at 25 °C, which transforms photoluminescent (PL)-inactive CdSe magic-size clusters (MSCs) to PL-active ones. The PL-inactive CdSe MSCs display an absorption doublet peaking at 421/450 nm. With a similar absorption doublet, the resulting PL-active CdSe/ZnSe MSCs exhibit a sharp PL signal at 460 nm. It is argued that the Zn-Se bond formation is decoupled from the growth of the ZnSe shell, which proceeds via the addition of ZnSe monomers. The chemical transformation at room temperature implements the principle of isodesmic reactions where M-Se bonds cleaved in the reactant are similar to those formed in the product. The present study paves an avenue for surface passivation under mild conditions, providing an in-depth understanding of the shell formation mechanism., (© 2024 Wiley‐VCH GmbH.)

In this work, electron microscopic studies of semiconductor compounds based on PbTe with impurities of dispersed CdSe phases have been carried out. As shown by the research results, in the initial undoped PbTe compound, the content of lead atoms is about 63,8 wt.%, and the tellurium content was 36,2 wt.%, i.e. corresponded to the stoichiometric composition. According to the electron microscope images, these components are evenly distributed over the area. The results of the study also showed that the formed new phases had grain sizes from 90 nm to 2 μm. The obtained values of the lattice parameter for the lead telluride compound and crystal system are in good agreement with the literature data. The structure of the resulting phases has the same symmetry as the initial undoped PbTe compound, a face-centered cubic lattice with the Fm3m symmetry class. In the molecules of the newly formed phases, in which the abundances of the elements Cd and Se prevailed, a change in the crystal lattice syngony was found.

In this paper, we attempted to improve the detection sensitivity of an indirect x-ray detector through using a hybrid active layer composed of a poly [N-90-heptadecanylâ€"2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) organic semiconductor and cadmium selenide nanoplatelets (CdSe NPLs) colloidal inorganic semiconductors. First, different blending ratio in the active layer (i.e. 2:1, 1:1, 1:2 and 1:3) of PCDTBT:CdSe NPL were examined, a sensitivity of 89.5 ÎĽ C·Gyairâˆ'1·cmâˆ'2 was achieved using a 1:1 ratio due to the low series resistance (RS) and defect density in this configuration. Then, the oleic acid (OA) that was initially applied in the CdSe NPL surface was replaced with pyridine ligands, this was done because the pyridine ligand is a short-chain ligand that can help charge transfer by reducing the distance between NPLs in the active layer. In addition, an experiment was conducted to determine the optimal ligand exchange time. A detector with an PCDTBT:CdSe NPL active layer fabricated using pyridine ligand exchange achieved a sensitivity of 219.8 ÎĽ C·Gyairâˆ'1·cmâˆ'2 after an exchange time of 12 h, this is an improvement of 155% compared to the detector using a PCDTBT:CdSe NPL with the original OA ligands. Lastly, the optimal thickness for the PCDTBT:CdSe NPL active layer was investigated. The highest mobility of 7.60 × 10âˆ' 6 cm2/V·s was recorded after fabricating the layer using spin-coating at 1900 rpm, the highest sensitivity of 314.0 ÎĽ C·Gyairâˆ'1·cmâˆ'2 was also achieved under these conditions. Compared to the initial state of the detector, our modifications improved the sensitivity of the PCDTBT:CdSe NPL detector by 251%. [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) films were synthesized on glass substrates via chemical surface deposition (CSD) and chemical bath deposition (CBD) methods. Aqueous solutions of cadmium chloride, thiourea, sodium selenosulfate, trisodium citrate and ammonia hydroxide were used. Theoretical calculations of the boundary conditions for the formation of cadmium selenide and cadmium hydroxide were carried out in the cadmium-selenosulfate and cadmium-selenosulfate-citrate-ammonia systems. The phase composition, optical transmission spectra and surface morphology of deposited CdSe films were investigated. According to the X-ray analysis, the film samples are single phase and consist of CdSe compound in its typical cubic modification. The film surface is solid, smooth and has a small number of surface defects. The optical transmission of CdSe films increases in the investigated wavelength area from 340 to 900 nm. The transmission curves have bends in the 650 nm region, which is typical for cadmium selenide. The optical band gap values of CdSe films are found to be in the range of 1.82-1.88 eV. [ABSTRACT FROM AUTHOR]

The ambient metastability of the rock-salt phase in well-defined model systems comprising nanospheres or nanorods of cadmium selenide, cadmium sulfide, or both was investigated as a function of composition, initial crystal phase, particle structure, shape, surface functionalization, and ordering level of their assemblies. Our experiments show that these nanocrystal systems exhibit ligand-tailorable reversibility in the rock salt–to– zinc blende solid-phase transformation. Interparticle sintering was used to engineer kinetic barriers in the phase transformation to produce ambient-pressure metastable rock-salt structures in a controllable manner. Interconnected nanocrystal networks were identified as an essential structure that hosted metastable high-energy phases at ambient conditions. These findings suggest general rules for transformation-barrier engineering that are useful in the rational design of next-generation materials. [ABSTRACT FROM AUTHOR]

In this study, the photocatalytic degradation of Methylene Blue was investigated using CdSe nanoparticles. CdSe nanoparticles were synthesized via a simple method and were characterized by FTIR, XRD, FESEM, BET, DRS and EDS techniques. The photocatalytic performance of the CdSe nanoparticles was optimized using Response Surface Methodology (RSM) under visible light. The independent variables involved initial pH, MB concentration, photocatalyst dosage, and irradiation time were evaluated and the optimum photodegradation efficiency of MB dye removal was achieved ˜ 92.80% at pH = 8, 20 mgL−1 of MB concentration, 0.02 g 50 mL−1 of CdSe dosage, and 20 min of irradiation time. Also, the photodegradation of MB by CdSe is obeyed pseudo-first-order kinetic model (k = 0.038 min−1). The thermodynamic results revealed that the photocatalytic degradation of MB is spontaneous and endothermic. Also, the evaluation of various scavengers confirmed that the MB photodegradation was mainly done by photogenerated holes and hydroxyl radicals. [ABSTRACT FROM AUTHOR]

Non-specific binding (NSB) is one of the important issues in biosensing performance. Herein, we designed a strategy for removing non-specific binding including anti-mouse IgG antibody and bovine serum albumin (BSA) by utilizing anisotropic cadmium selenide tetrapods (CdSe TPs) in a vortex flow. The shear force on the tetrapod nanoparticles was increased by controlling the rotation rate of the vortex flow from 0 rpm to 1000 rpm. As a result, photoluminescence (PL) signals of fluorescein (FITC)-conjugated protein, anti-mouse IgG antibody-FITC and bovine serum albumin (BSA)-FITC, were reduced by 35% and 45%, respectively, indicating that NSB can be removed under vortex flow. In particular, simultaneous NSB removal and protein capture can be achieved even with mixture solutions of target antibodies and anti-mouse IgG antibodies by applying cyclic mode vortex flow on anisotropic CdSe TPs. These results demonstrate successfully that NSB can be diminished by rotating CdSe TPs to generate shear force under vortex flow. This study opens up new research protocols for utilization of anisotropic nanoparticles under vortex flow, which increases the feasibility of protein capture and non-specific proteins removal for biosensors. [ABSTRACT FROM AUTHOR]

A large-scale computer simulation of the process of electronic excitation transport in close-packed nanoclusters of cadmium selenide colloidal quantum dots of various dimensions—one-dimensional, two-dimensional, and three-dimensional—has been performed. Quantitative dependences of the transport efficiency on a set of parameters characterizing the quantum dots have been obtained and analyzed. It has been shown that nonluminescent quantum dots and the thickness of the ligand shell have the greatest influence. [ABSTRACT FROM AUTHOR]

Silicon‐based tandem solar cells are regarded as one of the most feasible ways to break the single‐junction Shockley–Queisser limit efficiency and further reduce the cost of solar electricity. Recently, wide‐bandgap (≈1.7 eV) perovskite solar cells have drawn intense research interest as the top cell for Si‐based tandem devices. Despite significant progress in device efficiency, the unsatisfactory stability of perovskites is still a huge concern. Besides halide perovskites, there are many inorganic semiconductors worthy of investigation. It is believed that cadmium selenide, a binary compound enjoying outstanding optoelectronic properties, high stability, and low cost, is very promising as the top cell for Si‐based tandem devices. Herein, the CdSe thin‐film solar cells that have been neglected for 3 decades are revisited. Using rapid thermal evaporation, high‐quality CdSe thin films with large grain size, high‐photoluminescence, small Stokes shift, and intrinsic n‐type conductivity are obtained. Furthermore, CdSe solar cells are redesigned and a champion efficiency of 6.00% is achieved. Through in‐depth analysis, it is identified that bulk and interface defects limit the open‐circuit voltage and hence device performance. This work highlights the great potential of CdSe solar cells as top cells for Si‐based tandem devices. [ABSTRACT FROM AUTHOR]

Cadmium selenide films were prepared at different volumes of dopant (Europium) concentration by electrostatic- spray-pyrolysis technique. Optical results reveal low absorption and reflection with a corresponding high transmission in the visible region. Strong blue-shift is observed for the band gap energy in all cases of growth, indicating quantum confinement effect. Scanning electron studies reveal relatively smooth surface with small- sized grains on the surface. XRD confirms the crystalline nature of the films having hexagonal (wurtzite) structure with reduction in crystallinity of the film at increased volume of dopant concentration. EDX analysis confirmed the growth of CdSe:Eu film. [ABSTRACT FROM AUTHOR]

CdSe-carbon nanodots modified magnetic Fe3O4 nanospheres (CdSe-NDs@C-NDs@Fe3O4) were synthesized by a simple hydrothermal technique and characterized by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) with mapping, and energy dispersive X-ray spectroscopy (EDX). The prepared material was used as a magnetic solid phase microextraction (MSPE) adsorbent to determine malachite green (MG). Pasteurized cow's milk was used as the carbon source to fabricate the carbon nanodots. The spectrophotometric determination of malachite green was performed at 625 nm. The parameters affecting the microextraction efficiency were optimized, including the pH (9.0), mass of adsorbent (5 mg), eluent type (0.1 M acetic acid in ethanol), eluent volume (0.75 mL), sample volume (10 mL), in addition to matrix studies. In order to evaluate the accuracy of the method, real samples were subjected to addition-recovery tests and the recovery values from 85% to 104% were obtained. The limits of detection (LOD) and quantitation (LOQ) of the developed method were 0.013 µg mL−1 and 0.042 µg mL−1, respectively. [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 effect of temperature on the rate of hole transfer from photoexcited quantum dots (QDs) is investigated by measuring the driving force dependence of the charge transfer rate for different sized QDs across a range of temperatures from 78 to 300 K. Spherical CdSe/CdS core/shell QDs were used with a series of ferrocene-derived molecular hole acceptors with an 800 meV range in electrochemical potential. Time-resolved photoluminescence measurements and photoluminescence quantum yield measurements in an integrating sphere were both performed from 78 to 300 K to obtain temperature-dependent rates for a series of driving forces as dictated by the nature of the molecular acceptor. For both QD sizes studied and all ligands, the Arrhenius plot of hole transfer exhibited an activated (linear) regime at higher temperatures and a temperature-independent regime at low temperatures. The extracted activation energies in the high-temperature regime were consistent across all ligands for a given QD size. This observation is not consistent with direct charge transfer from the QD valence band to the ferrocene acceptor. Instead, a model in which charge transfer is mediated by a shallow and reversible trap more accurately fits the experimental results. Implications for this observed trap-mediated transfer are discussed including as a strategy to more efficiently extract charge from QDs.

Resonance Raman excitation profiles have been measured for the longitudinal optical phonon in two sizes of CdS quantum dots and in CdSe/CdS core/shell quantum dots. In pure CdS, the resonance Raman cross section for the fundamental transition is sharply peaked around the lowest-energy excitonic transition and becomes weaker with higher-energy excitation even though the absorbance continues to increase to higher energies. This effect, also observed in earlier studies of CdSe quantum dots, is attributed largely to interferences among multiple excitonic transitions contributing to the resonance Raman polarizability. No variation in exciton-phonon coupling strength with exciton energy is required to explain the decrease in the ratio of the Raman cross section to absorption cross section at shorter wavelengths. In core/shell structures, the CdSe phonons are relatively strong when exciting on resonance with the lower excitonic transitions, in which the hole is largely localized to the CdSe core, but become nearly undetectable at excitation wavelengths >0.6 eV above the lowest exciton, where both electrons and holes are largely localized in the CdS shell. The CdS phonon Raman cross section exhibits a maximum 0.6-0.7 eV above the lowest exciton and then decreases at higher energies for the same reasons as in pure CdS. [ABSTRACT FROM AUTHOR]

Inverted type-I heterostructure core/crown quantum rings (QRs) are quantum-efficient luminophores, whose spectral characteristics are highly tunable. Here, we study the optoelectronic properties of type-I core/crown CdS/CdSe QRs in the zincblende phase—over contrasting lateral size and crown width. For this, we inspect their strain profiles, transition energies, transition matrix elements, spatial charge densities, electronic bandstructures, band-mixing probabilities, optical gain spectra, maximum optical gains, and differential optical gains. Our framework uses an effective-mass envelope function theory based on the 8-band k · p method employing the valence force field model for calculating the atomic strain distributions. The gain calculations are based on the density-matrix equation and take into consideration the excitonic effects with intraband scattering. Variations in the QR lateral size and relative widths of core and crown (ergo the composition) affect their energy levels, band-mixing probabilities, optical transition matrix elements, emission wavelengths/intensities, etc. The optical gain of QRs is also strongly dimension and composition dependent with further dependency on the injection carrier density causing the band-filling effect. They also affect the maximum and differential gain at varying dimensions and compositions. [ABSTRACT FROM AUTHOR]

We report simulation results for scanning tunneling spectroscopy of gold-tipped CdSe nanodumbbells of lengths ~27 Å and ~78 Å. Present results are based on Bardeen, Tersoff, and Hamann formalism that takes inputs from ab initio calculations. For the shorter nanodumbbell, the current-voltage curves reveal negative differential conductance, the characteristic of a tunnel diode. This behaviour is attributed to highly localized metal induced gap states that rapidly decay towards the center of the nanodumbbell leading to suppression in tunneling. In the longer nanodumbbell, these gap states are absent in the central region, as a consequence of which zero tunneling current is observed in that region. The overall current-voltage characteristics for this nanodumbbell are observed to be largely linear near the metal-semiconductor interface and become rectifying at the central region, the nature being similar to its parent nanorod. The cross-sectional heights of these nanodumbbells also show bias-dependence where we begin to observe giant Stark effect features in the semiconducting central region of the longer nanodumbbell. [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) demonstrates high potential as a top cell material for Si-based tandem applications. However, obtaining high-quality CdSe thin films presents a significant challenge. Additionally, the intrinsic n-type conduction of CdSe desires a well-matched wide bandgap p-type partner to form a p-n junction for efficient photovoltaic applications. Herein, the vapor transport deposition method is employed to fabricate CdSe thin films with large grain sizes (∼2 μm), high crystallinity (with (002) preferred orientation), and strong band-edge photoluminescence. Moreover, zinc telluride (ZnTe), a II-VI group compound showing a low lattice mismatch of <0.7 % with CdSe, is explored as a p-type layer to construct solar cells. The properties of ZnTe thin film have been extensively studied and analyzed. By studying the annealing temperature (300 °C–550 °C), we obtained ZnTe film with a wide bandgap of 2.17 eV and conductivity of 1.4 × 10−5 S cm−1. To further enhance the carrier density of the ZnTe film, we employ a Cu doping strategy involving treatment with varying concentrations of CuBr solution (0 mg mL−1, 1 mg mL−1, 2.5 mg mL−1, 10 mg mL−1). Ultimately, a power conversion efficiency (PCE) of 2.03 % is achieved in CdSe/ZnTe solar cells. This is a primary exploration of all-inorganic CdSe/ZnTe solar cells, proving their potential for photovoltaic applications. Further optimization is deserved to achieve higher PCE. • VTD method was successfully employed to produce high-quality CdSe thin films with large grain sizes, high crystallinity, and intense PL. • ZnTe films, exhibiting lattice mismatch of only 0.7 % with CdSe, were carefully chosen to fabricate all-inorganic CdSe/ZnTe solar cells. • A notable efficiency of 2.03 % was achieved for CdSe/ZnTe thin film solar cells through an annealing treatment and a CuBr doping strategy in ZnTe. [ABSTRACT FROM AUTHOR]

CuCl2 solutions of various molarities were used to treat CdSe thin films produced by RF magnetron sputtering. In-depth investigation on the impacts of this treatment on CdSe thin films were studied. The structural investigation revealed that all as-grown films exhibited the hexagonal phase peak at the (101) plane. The crystalline and grain sizes increased with CuCl2 treatment, reaching 114 nm for 0.1 M CuCl2-treated CdSe thin film. A granule-like morphology was seen on the treated films. Opto-electric study revealed that CuCl2 treatment improved CdSe film properties and tailored structural restrictions. The 0.30 M CuCl2 treatment was shown to be an important process parameter for the CdSe thin films, indicating its potential as a photovoltaic material. [ABSTRACT FROM AUTHOR]

A novel and facile post-mortem interval (PMI) biosensor was fabricated using a double-label strategy to detect the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) biomarker. A monoclonal anti-GAPDH antibody was immobilized on a surface label containing cadmium selenide quantum dots (CdSe QDs) on a cysteamine graphene oxide (Cys-GO) self-assembled monolayer. Glucose oxidase (GOx) was used as a signal label to conjugate with GAPDH. GAPDH recognition was achieved through the dissolution of the surface-attached CdSe QDs by hydrogen peroxide generated through GAPDH-conjugated GOx-catalyzed β-glucose oxidation. To enhance sensitivity, a competitive interaction was introduced between free and conjugated GAPDH to the active site of the anti-GAPDH antibody. The electrochemical response due to CdSe dissolution decreased proportionally with the concentration of free GAPDH. Differential pulsed voltammetry was conducted to determine the analytical characteristics of the immunosensor, including the limit of detection, linear dynamic range, target selectivity, system stability, and applicability toward the analysis of real samples. [ABSTRACT FROM AUTHOR]

Colloidal quantum wells, or nanoplatelets, show among the lowest thresholds for amplified spontaneous emission and lasing among solution-cast materials and among the highest modal gains of any known materials. Using solution measurements of colloidal quantum wells, this work shows that under photoexcitation, optical gain increases with pump fluence before rolling off due to broad photoinduced absorption at energies lower than the band gap. Despite the common occurrence of gain induced by an electron–hole plasma found in bulk materials and epitaxial quantum wells, under no measurement conditions was the excitonic absorption of the colloidal quantum wells extinguished and gain arising from a plasma observed. Instead, like gain, excitonic absorption reaches a minimum intensity near a photoinduced carrier sheet density of 2 × 1013 cm−2 above which the absorption peak begins to recover. To understand the origins of these saturation and reversal effects, measurements were performed with different excitation energies, which deposit differing amounts of excess energy above the band gap. Across many samples, it was consistently observed that less energetic excitation results in stronger excitonic bleaching and gain for a given carrier density. Transient and static optical measurements at elevated temperatures, as well as transient X-ray diffraction of the samples, suggest that the origin of gain saturation and reversal is a heating and disordering of the colloidal quantum wells which produces sub-gap photoinduced absorption. [ABSTRACT FROM AUTHOR]

In this work, a thin film of Cadmium selenide is deposited on fluorine tin oxide-coated glass substrate through a simplified 2-electrode electrodeposition technique. The performance of the as-deposited films is compared with its annealed counterparts at two different temperatures of 250 °C and 350 °C in air. The impacts of annealing on different physical characteristics of the prepared films were investigated with the help of an X-ray diffractometer (XRD), scanning electron microscopy, and UV–Vis spectrometer. Studies on the photoresponse characteristics of the deposited films were also carried out. Structural analysis was done to determine the lattice parameters, size of the crystallite, dislocation density, and microstrain, utilizing the data from XRD analysis which exhibits a predominant orientation of CdSe films along (002) direction and showed the presence of hexagonal nanocrystalline phase. Morphological analysis shows larger grains for 350 °C-annealed sample than the as-grown and the 250 °C-annealed sample. The analysis of the optical property confirms a higher absorption in the visible region and shows a band gap of 1.65 eV at the annealing temperature of 350 °C. The photoresponse characteristic recorded a responsivity of 109 × 10–2 A/W, detectivity of 192 × 108 Jones, and an external quantum efficiency of 253% for the same sample which is annealed at higher temperature. The calculated rise time and decay time from the transient current characteristics at different incident power intensities were found to be 4.4 s and 5.1 s, respectively. The I–V characterization curve of the 350 °C-annealed CdSe sample affirms a good photocurrent response demonstrating that the heat treatment on the electrodeposited CdSe films improves its photodetecting capability that can be exploited for photodetector device applications. [ABSTRACT FROM AUTHOR]

CdSe magic‐sized quantum dots (MSQDs) have been widely used as fluorescent probes in biological systems due to their excellent optical properties with a broader fluorescence spectrum and stable luminescence in biological media. However, they can be cytotoxic and alter the redox balance depending on the amounts of Cd2+ adsorbed on their surface. Thus, the present study aimed to evaluate whether increases in selenium concentration in the synthesis of CdSe‐MSQDs decrease the oxidative stress caused by Cd2+‐based quantum dots. CdSe‐MSQDs synthesized with different concentrations of selenium were investigated against oxidative stress in the brain of chicken embryos by examining total antioxidant capacity, lipid peroxidation, thiol, and glutathione contents, as well as the activities of glutathione peroxidase, superoxide dismutase (SOD), catalase (CAT), and glutathione reductase. In addition, the vascularization of the chorioallantoic membrane (CAM) analysis was performed. Higher selenium concentrations alter the surface defect levels (decrease free Cd2+) and controlled the oxidative effects of CdSe‐MSQDs by reducing the lipid peroxidation, restoring the glutathione defense system and the antioxidant enzymes SOD and CAT, and maintaining the vascular density of the CAM. The current findings reinforce the study of the effects of the presence of Cd2+ ions on the surface of quantum dots, changing toxicity, and aiming interesting strategies of nanomaterials in biological systems. [ABSTRACT FROM AUTHOR]