Synthesis Of CdSe Quantum Dots Research Articles

Highly Efficient CdSe Quantum Dot-Sensitized Solar Cells via a Facile SILAR Method: Dependence of the SILAR Cycles on Optical Properties and Photovoltaic Performance

This work emphasizes using CdSe as a sensitizer in quantum dot-sensitized solar cells (QDSSCs) due to its beneficial band alignment with TiO2, enhancing effective charge injection. This study presents highly efficient CdSe QDSSCs developed using the successive ionic layer adsorption and reaction (SILAR) method. The XRD analysis revealed a hexagonal crystal structure for the synthesized CdSe quantum dots (QDs) with an average particle size of 9.2 nm. Increasing the SILAR cycles from 3 to 5 showed a decrease in the energy bandgap, reducing it from 1.79 eV to 1.68 eV, as observed in the investigation of optical properties. The optimal photovoltaic performance of CdSe QDSSCs was achieved at 4 SILAR cycles, yielding a notable power conversion efficiency (PCE) of 6.77% (Jsc = 14.63 mA/cm2, Voc = 0.71 V, FF = 65.2%), which is higher than that of a previous report of SILAR-prepared CdSe QDSSCs.

Synthesis of CdSe Quantum Dots in Two Solvents of Different Boiling Points for Polymer Optical Fiber Technology.

Polymer materials find many applications in various industries. Efforts are being made to obtain structures with increasingly better properties. It is necessary not only to obtain new materials but also to modify existing structures. Such is the situation with polymer optical fibers. The widespread use of polymer optical fibers is impossible, due to their very high optical losses compared to glass optical fibers. The solution to this problem can be the manufacturing of polymer active optical fibers. Active fibers are the basic components of fiber optic amplifiers and lasers that allow the direct amplification of light inside the fiber. In order for their operation to be the most effective, it is necessary to use dopants. The most commonly used are lanthanide ions isolated from the polymer network, active organic dyes, and quantum dots. These dopants are characterized by very high luminescence and long glow times. Quantum dots of CdSe are made using two organic solvents that differ in boiling points-hexane (a low-boiling solvent with a boiling point of 69 °C) and 1-octadecene (a high-boiling solvent with a boiling point of 315 °C). This work aims to test whether the type of solvent used to obtain quantum dots affects the doping capabilities of polymer structures, from which optical fibers can then be drawn.

Bright photoluminescence from CdSe quantum dots conjugated with metal phthalocyanines

Engineering organic/inorganic nanohybrids is one of the emerging tracks in material science to search for new nanomaterials with tailored and/or enhanced properties. In this work, we report the synthesis of CdSe quantum dots (QDs) conjugated with selected metal phthalocyanine (MPc), e.g., ZnPc and CuPc, utilizing the hot-injection organometallic method. The prepared pristine and conjugated QD systems exhibit practically identical particle size and spherical morphology and feature the characteristic CdSe excitonic peaks in their optical absorption spectra. The successful incorporation of ZnPc or CuPc molecules is ensured by the appearance of their sharp Q-band peaks in the optical absorption and the Zn2p or Cu2p core levels in the X-ray photoemission spectroscopy (XPS) measurements. The pure CdSe QDs sample of selected size (∼4.0 nm) exhibits well-defined photoluminescence (PL) peak at the limit of the green range, which is remarkably enhanced for the conjugated QD systems, reaching ∼250 % for the CuPc/CdSe QDs. Such prominent PL enhancement is attributed to Förster resonance energy transfer stimulated by deep B-band emissions from CuPc molecules combined with charge transfer from MPc molecules to CdSe QDs. Furthermore, the emission is greatly amplified upon prolonged exposure to laser beam, exceeding 400 % of the initial CuPc/CdSe emission after only 40 min of exposure time, yet without significant changes in their emission color. Thus, these MPc/CdSe conjugated QD systems are promising nanomaterials for intense white light sources.

Acid selenites as new selenium precursor for CdSe quantum dot synthesis

Chemical precursors for nanomaterials synthesis have become essential to tune particle size, composition, morphology, and unique properties. New inexpensive precursors investigation that precisely controls these characteristics is highly relevant. We studied new Se precursors, the acid selenites (R–O–SeOOH), to synthesize CdSe quantum dots (QDs). They were produced at room temperature by the ▪ reaction with alcohols having different alkyl chains and were characterized by 1H NMR confirming their structures. This unprecedented precursor generates high-quality CdSe nanocrystals with narrow size distribution in the zinc-blend structure showing controlled optical properties. Advanced characterization detailed the CdSe structure showing stacking fault defects and its dependence on the used R–O–SeOOH. The QDs formation was examined using a time-dependent growth kinetics model. Differences in the nanoparticle surface structure influenced the optical properties, and they were correlated to the Se-precursor nature. Small alkyl chain acid selenites generally lead to more controlled QDs morphology, while the bigger alkyl chain leads to slightly upper quantum yields. Acid selenites can potentially replace Se-precursors at competitive costs in the metallic chalcogenide nanoparticles. ▪ is chemically stable, and alcohols are cheap and less toxic than the reactants used today, making acid selenites a more sustainable Se precursor.

Digitizing protocols into single reactors for the one-pot synthesis of nanomaterials

Digitizing protocols into single reactors for the one-pot synthesis of nanomaterials

Effect of Different Ligands Coating on the Photovoltaic Performance of CdSe Quantum Dot-Sensitized Solar Cells

In this article, oleic acid (OA), oleylamine and tri-n-octylphosphine (OAm-TOP), and OA-TOP were used as ligands in the synthesis of CdSe quantum dots (QDs), respectively. Effect of three different ligands on the photovoltaic performance of CdSe QD-sensitized solar cells (QDSCs) is systematically investigated. Based on the results of UV-vis absorption spectra, it is confirmed that the absorption range is widen for CdSe QDs coated with OAm-TOP or OA-TOP compared with OA. Electrochemical impedance spectroscopy (EIS) study indicates that CdSe QDs synthesized using OAm-TOP or OA-TOP can better passivate the surface defects of QDs resulting in the improvement of photoelectric conversion efficiency (PCE) of devices. The optimized PCE of 3.6% was achieved for CdSe QDSCs modified with OAm-TOP.

Synthesis and photocatalytic activity of polymer stabilized cadmium selenide quantum dots-titanium dioxide nanocomposites

In this work, we report the synthesis of the nanocomposites of cadmium selenide (CdSe) quantum dots (QDs) and titanium dioxide nanoparticles (TiO2 NPs), and their use in the photocatalytic degradation of an organic dye. Titanium dioxide nanoparticles are a multifaceted large band gap metal oxide semiconductor that has been subjected to innumerable research studies in the past decades. TiO2 NPs exhibit characteristic properties depending upon their morphology, crystal structure, size and the method of synthesis that makes them suitable and efficient for different applications. The synthesized CdSe QDs were then used to sensitize TiO2 NPS in order to form CdSe QDs-TiO2 nanocomposites. The morphology of the QDs were investigated by high resolution-transmission electron microscopy. Fluorescence spectroscopy studies were performed to determine the absorption and emission peaks of the CdSe QDs. The band gap increased of pristine TiO2 NPs and CdSe decorated TiO2 NPs were evalued using UV–visible diffuse reflectance spectroscopy. The XRD pattern of the synthesized nanocomposites depicted the formation of anatase phase of TiO2. These nanocomposites were then used for the photocatalytic degradation of methylene blue (MB) dye.

Binding of Water‐Soluble CdSe Quantum Dots with Human Serum Albumin: Further Studies into their Effects on Dietary Polyphenol Binding and Sensing of Antibiotic Lomefloxacin

AbstractSynthesis of surface modified quantum dots (QDs) having potential biological activities are great important in biomedicinal chemistry. Here, we have synthesized mercapto propanoic acid (MPA) and thiolactic acid (TLA) coated water soluble cadmium selenide (CdSe) QDs having biological activity. Dispersion of QDs into a biological fluid can form protein corona. Hence, the binding of CdSe QDs with the carrier protein, human serum albumin (HSA) have been executed using spectroscopic methods. The binding affinity order of CdSe QDs‐HSA complexes were found in the order of 105 M−1 at 298 K. CdSe QDs are also affects the binding affinities of dietary polyphenols (naringin: NG and naringenin: NRG) towards HSA. The synthesized CdSe QDs was employed to sensing of antibiotic lomefloxacin by fluorescence quenching mechanism. The detection limit was found 0.70‐1.83 μg mL−1. The CdSe QDs also demonstrate the detection of lomefloxacin under uv light based on color change of the solutions.

Photocatalytic solar fuel production and environmental remediation through experimental and DFT based research on CdSe-QDs-coupled P-doped-g-C3N4 composites

Solar energy harvesting and conversion into useful chemical energy with the aid of semiconductor photocatalysts is a promising technique to solve both energy and environmental issues. This work reports a successful synthesis of CdSe quantum dots (QDs) modified phosphorus doped g-C3N4 (P-CN) for advanced photocatalytic applications. Phosphorus doping and structural coupling with CdSe QDs are shown to significantly extend visible-light response of g-C3N4 up to 700 nm. The optimized sample 4CdSe/P-CN demonstrates enhanced visible-light driven overall water splitting activities for H2 and O2 evolution i.e. 113 and 55.5 μmol.h−1. g−1, respectively, as well as very high photocatalytic CO2 to CH4 conversion efficiency (47 μmol.h−1. g−1). It also exhibit higher activity (78 %) for 2,4-dichlorophenol degradation as compared to pristine CN-sample. Combined photoluminescence, transient/single wavelength photocurrent, photoelectrochemical, and coumarin fluorescence spectroscopy demonstrate that 4CdSe/P-CN nanocomposite exhibit enhanced charge separation efficiency which is responsible for improved visible light catalytic activities. Our work thus provide a new strategy to design low-cost and sustainable photocatalysis with wide visible-light activity for practical overall water splitting and CO2 reduction applications.

Chitosan/P3HT biohybrid films as polymer matrices for the in‐situ synthesis of CdSe quantum dots. Experimental and theoretical studies

AbstractBiohybrid nanocomposite films were obtained through a simple two‐step methodology. Films of chitosan/poly(3‐hexylthiophene) (CS/P3HT) were used as polymer matrices for the in‐situ synthesis and stabilization of CdSe quantum dots. The biohybrid materials were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), Raman spectroscopy, UV–visible spectroscopy, thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), high‐resolution transmission electron microscopy (HRTEM), and photoluminescence spectroscopy (PL). The effects of the P3HT composition on the properties of the QDs in the films were analyzed. The results confirmed that CS/P3HT films provided an adequately confining matrix for the growth of CdSe QDs with a fairly uniform size and revealed that the interactions between the CdSe nanoparticles and the CS/P3HT matrix mainly involved the OH and NH2 groups. The optical band gaps of the biohybrid nanocomposite films were estimated. The results of photoluminescence revealed that a charge transfer phenomenon occurred in the polymer system. Finally, theoretical analyses suggest that the CdSe QDs would be preferentially located onto the chitosan domains.

The synthesis of CdSe quantum dots stabilized by polymers and polyelectrolyte capsules

The formation of nanocomposites based on quantum dots and polymers is a way of combining the benefits of quantum dots, such as their fundamental novelty and biomedical perspectives, with technological capabilities of polymers. The aim of this work was to synthesize cadmium selenide (CdSe) quantum dots in the presence of polymers (polyethyleneimine and chitosan) in an aqueous solution and embed cadmium selenide/polymer nanoparticles into polyelectrolyte capsules. To characterize the polymer-stabilized cadmium selenide quantum dots, the authors used fluorescence spectroscopy and dynamic and electrophoretic light scattering methods. The morphology of cadmium selenide/polymer nanoparticles characterized by the method of transmission electronic microscopy. The incorporation of quantum dots into a polymer matrix can significantly reduce their toxicity and prolong the duration of their fluorescence signals. Cadmium selenide nanoparticles stabilized by chitosan were used to synthesize five-layered polyelectrolyte capsules.

The biosynthesis of cadmium selenide quantum dots by Rhodotorula mucilaginosa PA-1 for photocatalysis

CdSe quantum dots (QDs) are semiconductor materials and possess unique optical and electronic properties, therefore being increasingly used in many fields. Biosynthesis of CdSe QDs has several advantages over the chemical synthesis route. In this study, the CdSe QDs were biosynthesized using a yeast Rhodotorula mucilaginosa PA-1 under the aerobic condition. The regulation of QDs biosynthesis was achieved by changing the concentration of precursors and the pH of the medium. The concentration of cadmium ions but not selenium ions determined the synthesis of CdSe QDs. Synthesized CdSe QDs with a narrow size distribution (3.2 ± 0.4 nm) exhibited great photocatalytic activity under ultraviolet and visible light using a dye malachite green (MG) as a model pollutant. The photocatalytic degradation efficiency of MG was 86.5 % and 94.28 % after 60 min irradiation under ultraviolet and visible light, respectively, which is comparable for those catalyzed by various nanomaterials through chemical synthesis.

CdSe quantum dots (QDs) were synthesized by a hot-bubbling strategy

A hot-bubbling strategy was studied to synthesize CdSe quantum dots. The synthetic parameters including temperature and growth time, were studied to show great influence on the optical properties. At the different reaction time CdSe quantum dots could emit fluorescence of different color, ranging from green to red, under the ultraviolet lamp which had irradiation of 365nm. The size of CdSe quantum dots was adjusted by the temperature and reaction time. CdSe quantum dots with sphalerite structure were prepared by this method.

Formation of CdSe quantum dots from single source precursor obtained by thermal and laser treatment

The synthesis of CdSe quantum dots (QDs) from a single source precursor is a known way to form a nanocomposite by its thermal decomposition. Recently, some of them have been used to grow QDs by direct laser patterning. Here, the authors report the study of the formation of the CdSe QDs starting from the decomposition of the 2-(N,N-dimethylamino)ethylselenolate of cadmium dispersed in a polymethylmethacrylate film induced both by heating and laser patterning. The formation of the CdSe QDs under annealing at 150 °C is studied as a function of the precursor concentration and molar ratio with respect to two different QD ligands such as oleic acid and oleylamine. The photoluminescent spectra of the formed nanocomposite show that the oleic acid induces the formation of the direct bandgap, while oleylamine shows only a broadband emission. The laser patterning of the film was carried out with a UV laser (355 nm) with a pulse frequency of 40 kHz and a fluence of 1.06 J/cm2. The resulting patterned areas were characterized by a fluorescence microscope showing the formation of a photoluminescence path only when the ligands were present, suggesting the formation of the functional (photoluminescent) QDs.

On-Demand Sonochemical Synthesis of Ultrasmall and Magic-Size CdSe Quantum Dots in Single-Phase and Emulsion Systems.

The sonochemical synthesis of CdSe quantum dots (QDs) in a single-liquid bulk phase and in an emulsion-based system is presented. Reactions utilized cadmium oleate and trioctylphosphine selenide precursors and were monitored as a function of sonication time under controlled temperature conditions to isolate the effects of cavitation from those of bulk temperature changes. QD synthesis was found to be slow in the single-phase liquid system (i.e., 1-octadecene) but greatly accelerated in the dispersed system (i.e., emulsions of 1-octadecene in ethylene glycol). It is hypothesized that the emulsion system increases the cavitation efficiency while also delivering acoustic energy in closer proximity to the precursor molecules. The capacity of CdSe production in the emulsion system was found to be 3.8 g/(L h), which is comparable to the typical hot-injection synthesis of CdSe QDs and can likely be further optimized. While the single-phase solvent system was found to produce ultrasmall QDs that exhibit broadband white-light emission, the emulsion system was found to produce well-defined magic-size clusters (MSCs) with photoluminescence quantum yield as high as 34%. Differences in synthesis rate and product properties from the emulsion and single-phase systems were probed by X-ray diffraction, electron microscopy, UV-visible (vis) and photoluminescence spectroscopy, and small-angle X-ray scattering (SAXS). Finally, precise temporal control of the QD synthesis was demonstrated via on-off cycling of the ultrasound waves.

Kolloidal CdSe Kuantum Noktalarının Sentezi ve Optik Karakterizasyonu

Colloidal CdSe quantum dots were nucleated at about 300oC for 15 s and growth at 272oC up to 245 min in non-coordinating solvent octadecene by using hot-injection technique. Stearic acid was used as a capping agent in the synthesis of CdSe quantum dots. The nucleation time used in this study was considerably longer than those in the literature and its effect on the optical properties was examined. The first excitonic absorption and corresponding recombination peaks were observed in their optical absorption and photoluminescence spectra, respectively. The value of Stokes shift changed up to 70 meV. A peak and shoulder structure was obtained in the optical absorption and photoluminescence spectra of the sample growth for 20 min. It was indicated that CdSe quantum dots which are nucleated at high temperature for a sufficiently long period may have double size distribution. The images of CdSe quantum dots were obtained via transmission electron microscopy. Their images were processed with the image processing program ImageJ. The average size of CdSe quantum dots growth for 12 min was found as 2.63 nm. The size dispersion increased 4.6 times with respect to that of the monodisperse quantum dots. The X-ray energy transition peaks belong to Cd and Se elements were observed in their energy dispersive X-ray spectra. Symmetric and asymmetric vibrational modes of stearic acid molecules capping these quantum dots were determined at about 2848 cm-1 and 2914 cm-1 , respectively, by using Fourier transform infrared spectroscopy.

Novel Synthesis of CdSe Quantum Dots in a Confined Space by Using a High Internal Phase Emulsion and Their Application in Fluorescent Labeling

AbstractThe synthesis of CdSe quantum dots (QDs) in a confined space constructed by the aqueous continuous phase of high internal phase emulsion (HIPE) at room temperature was proposed, and the obtained high quality QDs was applied as the label of amino groups in epoxy resin. In a typical system of oil‐in‐water HIPE, the aqueous solution film containing selenium powder, cadmium chloride, and 3‐mercaptopropionic acid was squeezed by the droplet of toluene and acted as a nano‐reactor, and then QDs nanoparticles with high fluorescence intensity were generated at room temperature. The morphologies of HIPE containing QDs were observed by fluorescence microscopy, and the QDs product were characterized by high‐resolution transmission electron microscopy and UV‐vis Spectrophotometer. The effect of the confined space, including the stability, the dimension of continuous phase, and the interface structure of HIPE, on the fluorescence performance of QDs were investigated. Furthermore, the mechanism of ‘temporary ligand’ was proposed to explain the better performance of QDs prepared at the introduction of ionic emulsifier. Finally, attributed to the inherent carboxylic end ligands of obtained QDs, it is applied to mark the amino curing agent in the epoxy resin, and the visualized observation of the dispersion of amino curing agent in epoxy matrix was realized.

Synthesis, Structural and Optical Investigation of CdSe semiconductor Quantum Dots

In this paper, we present a simple synthetic route for the development of high quality CdSe quantum dots TGA capped in aqueous solutions. CdSe semiconducting Quantum dots were prepared by a chemical method at room temperature. The crystal structure, morphology, spectral and compositional properties were analyzed from powder X-ray Diffraction, High resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV-Vis absorbance and Photoluminescence (PL), Fourier transform infrared (FTIR) and Fourier transform RAMAN (FT-RAMAN) techniques. The XRD results depicted the formation of CdSe quantum dots with the average crystallite size of 3 nm and 4 nm, which is in accordance with observations from HRTEM and TEM micrographs predict an average particle diameter of the QDs range between 2-3 nm. The UV-Vis absorbance peaks indicate the broad absorption behavior of the synthesized CdSe quantum dots. The calculated band gap energy was 2.55 eV and further it is found the particle size estimated from the maximum excitonic peaks for CdSe 2.7 nm. The photoluminescence studies evidenced that the luminesce property of quantum dots can be varied by systematically tuning precursor concentrations. The PL emission spectrum depicts the strong excitation peaks for the synthesized CdSe QDs with peaks centered at 603 nm. The capping of TGA was confirmed from FTIR and FT-RAMAN studies. From the FTIR spectra it is observed that, for the synthesized CdSe QDs almost all the peaks are common with slightly shifting behavior towards larger and shorter wave numbers. FT-Raman analysis was performed to study the sample qualities such as microcrystallinity, homogeneity and surface conditions for the as synthesized CdSe quantum dot. The resulting colloids are very stable, and no precipitate is observed over a period of 6 months.

Facile Access to Wearable Device via Microfluidic Spinning of Robust and Aligned Fluorescent Microfibers.

Microfluidic spinning technology (MST) has drawn much attention owing to its ideal platform for ordered fluorescent fibers, along with their large-scale manipulation, high efficiency, flexibility, and environment friendliness. Here, we employed the MST to fabricate a series of uniform fluorescent microfibers. By adjusting the microfluidic spinning parameters, the as-prepared microfibers of different diameters are successfully obtained. For more practice, these regular arranged fibers could be formed to versatile fluorescent codes by using various microfluidic chips. Also, these versatile fluorescent fibers could be further weaved into a white fluorescent film via continuous and cross-spinning process, which could be applied in a white light emitting diode (WLED) and a wearable device. Besides, we investigated the MST-directed microreactors to carry out green synthesis of CdSe quantum dots (QDs) fibers by the knot of Y-type microfluidic chip. The as-prepared CdSe QDs show nice optical property and are good candidate as phosphors in WLED. This strategy offers a facile and environment-friendly route to fluorescent hybrid microfibers and might open their potential application in optical devices, security, and fluorescent coding.

Facile and green synthesis of 1-thioglycerol capped CdSe quantum dots in aqueous solution

CdSe quantum dots (QDs) have been synthesized in aqueous solutions of Cd(NH3)4SO4 and Na2SeSO3 in the presence of 1-thioglycerol at ambient conditions. These QDs were found to exhibit very sharp excitonic absorption peak between 400 and 430 nm and a second peak at around 360 nm and exhibit very broad fluorescence in the entire visible range with a large stokes shift. The QDs were monodisperse and stable under ambient conditions for several months. Their optical properties were found to have a strong correlation with the stoichiometric ratios of Cd:Se. 1-Thioglycerol was found to play a dual role in the synthesis of CdSe QDs, (i) catalyses the reaction to form CdSe and (ii) acts as a capping agent for these QDs. An in depth study of their electrochemical analysis have been made and a probable reaction mechanism for the formation of these QDs has been provided.