Ultrathin CdSe/CdS and CdSe/ZnS core-shell nanoplatelets: The impact of the shell material on the structure and optical properties

2019 ◽  
Vol 209 ◽  
pp. 170-178 ◽  
Author(s):  
B.M. Saidzhonov ◽  
V.F. Kozlovsky ◽  
V.B. Zaytsev ◽  
R.B. Vasiliev
Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 333 ◽  
Author(s):  
Julia Kredel ◽  
Christian Dietz ◽  
Markus Gallei

The preparation of highly ordered colloidal architectures has attracted significant attention and is a rapidly growing field for various applications, e.g., sensors, absorbers, and membranes. A promising technique for the preparation of elastomeric inverse opal films relies on tailored core/shell particle architectures and application of the so-called melt-shear organization technique. Within the present work, a convenient route for the preparation of core/shell particles featuring highly fluorinated shell materials as building blocks is described. As particle core materials, both organic or inorganic (SiO2) particles can be used as a template, followed by a semi-continuous stepwise emulsion polymerization for the synthesis of the soft fluoropolymer shell material. The use of functional monomers as shell-material offers the possibility to create opal and inverse opal films with striking optical properties according to Bragg’s law of diffraction. Due to the presence of fluorinated moieties, the chemical resistance of the final opals and inverse opals is increased. The herein developed fluorine-containing particle-based films feature a low surface energy for the matrix material leading to good hydrophobic properties. Moreover, the low refractive index of the fluoropolymer shell compared to the core (or voids) led to excellent optical properties based on structural colors. The herein described fluoropolymer opals and inverse opals are expected to pave the way toward novel functional materials for application in fields of coatings and optical sensors.


2014 ◽  
Vol 70 (a1) ◽  
pp. C1583-C1583
Author(s):  
Rainer Lechner ◽  
Gerhard Fritz-Popovski ◽  
Maksym Yarema ◽  
Wolfgang Heiss ◽  
Armin Hoell ◽  
...  

The chemical synthesis of core/shell colloidal nanocrystals (NCs) have lead to an pronounced improvement in the optical properties and the chemical stability of semiconducting NCs [1]. The main topic of this work is the structural characterisation of core/shell NCs with anomalous small angle x-ray scattering (ASAXS) in combination with diffraction techniques (XRD) at laboratory- and synchrotron sources (HZB-BESSY and ESRF). Furthermore we complete these findings with complementary microscopy techniques (TEM). The detailed knowledge of the structural properties of the core/shell NCs allows to study the impact of the nanometer sized dimensions on their optical properties. The infrared emission of lead chalcogenide nanocrystals (NCs) in the size range of 5 - 10 nm can be drastically increased stabilising the core with a hard protective shell [1,2]., e.g., PbS/CdS NCs shows a higher efficiency and stability [2] with respect to pure PbS-NCs. In contrast to a shell growth on top of a core, we investigated in this study the CdS-shell growth on PbS NCs driven by Cd for Pb cation exchange [2]. Especially, we studied three different final shell thicknesses of 0.9, 1.5 and 2 nm. The chemical composition profile of the CdS-shell as a function of reaction time are derived from ASAXS experiments in sub-nanomter resolution. The crystal structure of the shell was derived by XRD combined with TEM measurements, respectively. We relate the chemical and structural information to the measured PL intensities of the core/shell NCs. We reveal the existence of two different crystalline phases, i.e. the metastable rock salt and the equilibrium zinc blende phase within the chemically pure CdS-shell. The highest improvement in the PL emission was achieved for 0.9 nm shells depicting a large metastable rock salt phase fraction matching the crystal structure of the PbS core. These results could be only achieved using ASAXS that gieves a mean chemical profile of a large ensemble of single core/shell NCs, but in sub-nanometer resolution [3].


Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1570
Author(s):  
Shujahadeen B. Aziz ◽  
Elham M. A. Dannoun ◽  
Dana A. Tahir ◽  
Sarkawt A. Hussen ◽  
Rebar T. Abdulwahid ◽  
...  

In the current study, polymer nanocomposites (NCPs) based on poly (vinyl alcohol) (PVA) with altered refractive index and absorption edge were synthesized by means of a solution cast technique. The characterization techniques of UV–Vis spectroscopy and XRD were used to inspect the structural and optical properties of the prepared films. The XRD patterns of the doped samples have shown clear amendments in the structural properties of the PVA host polymer. Various optical parameters were studied to get more insights about the influence of CeO2 on optical properties of PVA. On the insertion of CeO2 nanoparticles (NPs) into the PVA matrix, the absorption edge was found to move to reduced photon energy sides. It was concluded that the CeO2 nanoparticles can be used to tune the refractive index (n) of the host polymer, and it reached up to 1.93 for 7 wt.% of CeO2 content. A detailed study of the bandgap (BG) was conducted using two approaches. The outcomes have confirmed the impact of the nanofiller on the BG reduction of the host polymer. The results of the optical BG study highlighted that it is crucial to address the ɛ” parameter during the BG analysis, and it is considered as a useful tool to specify the type of electronic transitions. Finally, the dispersion region of n is conferred in terms of the Wemple–DiDomenico single oscillator model.


RSC Advances ◽  
2021 ◽  
Vol 11 (42) ◽  
pp. 26218-26227
Author(s):  
R. Panda ◽  
S. A. Khan ◽  
U. P. Singh ◽  
R. Naik ◽  
N. C. Mishra

Swift heavy ion (SHI) irradiation in thin films significantly modifies the structure and related properties in a controlled manner.


Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 359
Author(s):  
Francesco Ruffino

Bimetallic nanoparticles show novel electronic, optical, catalytic or photocatalytic properties different from those of monometallic nanoparticles and arising from the combination of the properties related to the presence of two individual metals but also from the synergy between the two metals. In this regard, bimetallic nanoparticles find applications in several technological areas ranging from energy production and storage to sensing. Often, these applications are based on optical properties of the bimetallic nanoparticles, for example, in plasmonic solar cells or in surface-enhanced Raman spectroscopy-based sensors. Hence, in these applications, the specific interaction between the bimetallic nanoparticles and the electromagnetic radiation plays the dominant role: properties as localized surface plasmon resonances and light-scattering efficiency are determined by the structure and shape of the bimetallic nanoparticles. In particular, for example, concerning core-shell bimetallic nanoparticles, the optical properties are strongly affected by the core/shell sizes ratio. On the basis of these considerations, in the present work, the Mie theory is used to analyze the light-scattering properties of bimetallic core–shell spherical nanoparticles (Au/Ag, AuPd, AuPt, CuAg, PdPt). By changing the core and shell sizes, calculations of the intensity of scattered light from these nanoparticles are reported in polar diagrams, and a comparison between the resulting scattering efficiencies is carried out so as to set a general framework useful to design light-scattering-based devices for desired applications.


Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1728
Author(s):  
Joshua Fernandes ◽  
Sangmo Kang

The near-field enhancement and localized surface plasmon resonance (LSPR) on the core-shell noble metal nanostructure surfaces are widely studied for various biomedical applications. However, the study of the optical properties of new plasmonic non-spherical nanostructures is less explored. This numerical study quantifies the optical properties of spherical and non-spherical (prolate and oblate) dimer nanostructures by introducing finite element modelling in COMSOL Multiphysics. The surface plasmon resonance peaks of gold nanostructures should be understood and controlled for use in biological applications such as photothermal therapy and drug delivery. In this study, we find that non-spherical prolate and oblate gold dimers give excellent tunability in a wide range of biological windows. The electromagnetic field enhancement and surface plasmon resonance peak can be tuned by varying the aspect ratio of non-spherical nanostructures, the refractive index of the surrounding medium, shell thickness, and the distance of separation between nanostructures. The absorption spectra exhibit considerably greater dependency on the aspect ratio and refractive index than the shell thickness and separation distance. These results may be essential for applying the spherical and non-spherical nanostructures to various absorption-based applications.


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