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Synthesis of dot in rod semiconductor heterostructures for the engineering of nanocrystals optical properties
No full textThis paper focuses on a preliminary study based on a two-steps approach to produce complex core/multiple shell architectures, such as “dots-in-rods” (DRs), to be exploited as color down-conversion filters for display
manufacturing. Core/shell CdSe/CdS DRs are prepared by using a conventional fast hot injection reaction method to grow CdS layers onto CdSe QDs cores. Then, the CdSe/CdS DRs are engineered by growing an additional CdS shell coated by oleate (OA) molecules, thus producing CdSe/CdS@CdS/OA DRs. This further hybrid shell is synthesized by
means of a seeded-growth approach, consisting of the controlled injection of TOP-S and cadmium oleate (Cd(OA)2) as sulfur and cadmium precursors, respectively. As assessed by transmission electron microscopy (TEM) and UV-Vis absorption and photoluminescence (PL) spectroscopies analyses, the feasibility to control the amount of precursors allows to modulate the thickness of the further hybrid shells and therefore the morphological and optical properties of the final heterostructures. The introduction of further shells grafted by specific organic ligand improves the solubility in
polymeric matrices. This condition is crucial to produce hybrid nanocomposite films that can be integrated in display manufacturing applications. Moreover, the capability of the final CdSe/CdS@CdS/OA nanostructures to convert blue
light in red wavelengths with a remarkable photoluminescence quantum yields (PLQY) makes the produced materials the ideal candidates for a variety of optoelectronic applications, particularly for the fabrication of color down-conversion filters
Direct Laser Patterning of CdTe QDs and Their Optical Properties Control through Laser Parameters
Full text linkDirect laser patterning is a potential and powerful technique to localize nanomaterials within a host matrix. The main goal of this study is to demonstrate that by tuning some parameters of a laser source, like power and laser pulse frequency, it is possible to modify and tune the optical properties of the generated quantum dots (QDs) within a host matrix of a specific chemical composition. The study is realized by using cadmium telluride (CdTe) QD precursors, embedded in polymethylmethacrylate (PMMA) host matrix, as starting materials. The patterning of the CdTe QDs is carried out by using a UV nanosecond laser source at 355. Fluorescence microscopy and photoluminescence spectroscopy, associated with transmission electron microscopy, indicate that it is possible to obtain desired patterns of QDs emitting from green to red of the visible spectrum, due to the formed CdTe QDs. Preliminary highlights of the CdTe QDs’ formation mechanism are given in terms of laser power and laser pulse frequency (repetition rate)
Cadmium telluride nanocomposite films formation from thermal decomposition of cadmium carboxylate precursor and their photoluminescence shift from green to red
No full textThis study focuses on the investigation of a CdTe quantum dots (QDs) formation from a cadmium-carboxylate precursor, such as cadmium isostearate (Cd(ISA)2), to produce CdTe QDs with tunable photoluminescent (PL) properties. The CdTe QDs are obtained by the thermal decomposition of precursors directly in the polymer matrix (in situ method) or in solution and then encapsulated in the polymer matrix (ex situ method). In both approaches, the time course of the CdTe QDs formation is followed by means of optical absorption and PL spectroscopies focusing on viable emission in the spectral interval between 520 and 630 nm. In the polymeric matrix, the QDs formation is slower than in solution and the PL bands have a higher full width at half maximum (FWHM). These results can be explained on the basis of the limited mobility of atoms and QDs in a solid matrix with respect to the solution, inducing an inhomogeneous growth and the presence of surface defects. These achievements open the way to the exploitation of Cd(ISA)2 as suitable precursor for direct laser patterning (DPL) for the manufacturing of optoelectronic devices
Cadmium telluride nanocomposite films formation from thermal decomposition of cadmium carboxylate precursor and their photoluminescence shift from green to red
No full textThis study focuses on the investigation of a CdTe quantum dots (QDs) formation from a cadmium-carboxylate precursor, such as cadmium isostearate (Cd(ISA)(2)), to produce CdTe QDs with tunable photoluminescent (PL) properties. The CdTe QDs are obtained by the thermal decomposition of precursors directly in the polymer matrix (in situ method) or in solution and then encapsulated in the polymer matrix (ex situ method). In both approaches, the time course of the CdTe QDs formation is followed by means of optical absorption and PL spectroscopies focusing on viable emission in the spectral interval between 520 and 630 nm. In the polymeric matrix, the QDs formation is slower than in solution and the PL bands have a higher full width at half maximum (FWHM). These results can be explained on the basis of the limited mobility of atoms and QDs in a solid matrix with respect to the solution, inducing an inhomogeneous growth and the presence of surface defects. These achievements open the way to the exploitation of Cd(ISA)(2) as suitable precursor for direct laser patterning (DPL) for the manufacturing of optoelectronic devices
Formation of CdSe quantum dots from single source precursor obtained by thermal and laser treatment
No full textThe 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 degrees 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 (355nm) with a pulse frequency of 40kHz and a fluence of 1.06J/cm(2). 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
Magnetic carbon spheres and their derivatives combined with printed electrochemical sensors
Full text linkHerein, we report the synthesis of several magnetic carbon structures starting from spheres (CSs) to more elongated structures to get tubes and fibers by customizing chemical vapour deposition parameters. These CSs-based products, ranging from nano-to micro-size, were investigated by morphological point of view using scanning electron microscopy, energy dispersive x-ray spectroscopy, and Raman spectroscopy. These carbon structures were combined with screen-printed electrodes highlighting their electrochemical effectiveness towards the detection of several species, i.e. ferricyanide, ascorbic acid, dopamine, cysteine, serotonin, and NADH. The presence of iron nuclei within the carbonaceous lattices, besides having improved the electrochemical performances at the printed electrodes, might confer these CSs-based structures a future application in the field of remediation/sensing. Herein, some preliminary applications were provided showing that these materials can be easily employed to collect species and, successively, coupled with printed electrochemical sensors
Synthesis of dot in rod semiconductor heterostructures for the engineering of nanocrystals optical properties
Full text linkThis paper focuses on a preliminary study based on a two-steps approach to produce complex core/multiple shell architectures, such as “dots-in-rods” (DRs), to be exploited as color down-conversion filters for display manufacturing. Core/shell CdSe/CdS DRs are prepared by using a conventional fast hot injection reaction method to grow CdS layers onto CdSe QDs cores. Then, the CdSe/CdS DRs are engineered by growing an additional CdS shell coated by oleate (OA) molecules, thus producing CdSe/CdS@CdS/OA DRs. This further hybrid shell is synthesized by means of a seeded-growth approach, consisting of the controlled injection of TOP-S and cadmium oleate (Cd(OA)2) as sulfur and cadmium precursors, respectively. As assessed by transmission electron microscopy (TEM) and UV-Vis absorption and photoluminescence (PL) spectroscopies analyses, the feasibility to control the amount of precursors allows to modulate the thickness of the further hybrid shells and therefore the morphological and optical properties of the final heterostructures. The introduction of further shells grafted by specific organic ligand improves the solubility in polymeric matrices. This condition is crucial to produce hybrid nanocomposite films that can be integrated in display manufacturing applications. Moreover, the capability of the final CdSe/CdS@CdS/OA nanostructures to convert blue light in red wavelengths with a remarkable photoluminescence quantum yields (PLQY) makes the produced materials the ideal candidates for a variety of optoelectronic applications, particularly for the fabrication of color down-conversion filters
FIGURE 7 from paper JVST-B "Formation of CdSe quantum dots from single source precursor obtained by thermal and laser treatment"
No full textThe dataset includes two files: the word file describes the type of sample and the procedures used to pick up the data; the excel file includes the raw data used to obtain the plots of figure 7.
In the following is reported the description of figure 7 as wrote in the paper.
(a) Bright-field and (b) fluorescence microscope images a 10Å~ magnification of films after the laser treatment
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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