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Rabih Al Rahal Al Orabi

Bio: Rabih Al Rahal Al Orabi is an academic researcher from Solvay. The author has contributed to research in topics: Dielectric & Percolation. The author has an hindex of 1, co-authored 2 publications receiving 5 citations.

Papers
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Journal ArticleDOI
TL;DR: Interaction of light with these novel semiconducting nanostructures hosting rare-earth emitters should be attractive for applications that require broadband sensitization of RE emitters.
Abstract: We report the synthesis of colloidal EuS, La2S3, and LaS2 nanocrystals between 150 and 255 °C using rare-earth iodides in oleylamine. The sulfur source dictates phase selection between La2S3 and LaS2, which are stabilized for the first time as colloidal nanocrystals. The indirect bandgap absorption of LaS2 shifts from 635 nm for nanoellipsoids to 365 nm for square-based nanoplates. Er3+ photoluminescence in La2S3:Er3+ (10%) is sensitized by the semiconducting host in the 390-450 nm range. The synthetic route yields tunable compositions of rare-earth sulfide nanocrystals. Interaction of light with these novel semiconducting nanostructures hosting rare-earth emitters should be attractive for applications that require broadband sensitization of RE emitters.

24 citations

Proceedings ArticleDOI
05 Jul 2020
TL;DR: In this article, the impact of the dispersion state of the nanoparticles on dielectric properties was evaluated with different dispersion states and polarization couplings were proposed to enhance the effective permittivity in aggregated systems and Maxwell-Wagner-Sillars polarization may also contribute at low frequencies due to local percolation of the particles.
Abstract: Polymer composites with PVdF-HFP matrix and BaTiO3 nanoparticles were prepared with different dispersion states to evaluate the impact of the dispersion state of the nanoparticles on dielectric properties. We observe that the dispersion state has two effects: first, the overall dielectric permittivity is a little higher in aggregated systems than in well-dispersed systems; Second, conductivity, together with a capacitive contribution, increase at low frequencies in aggregated systems as compared to well-dispersed systems. We propose that polarization couplings may enhance the effective permittivity in aggregated systems, and that Maxwell-Wagner-Sillars polarization may also contribute at low frequencies due to local percolation of the particles.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, a single unconjugated precursor, glucose, was used to synthesize carbonized polymer dots (CPDs), which can be used to construct multicolor fluorescent CPDs.
Abstract: Tunable emission carbonized polymer dots (CPDs) are highly desirable for the preparation of optoelectronic devices, especially white light-emitting diodes (WLEDs). In most available studies, polychromatic CPDs are synthesized using aromatic molecules as precursors. However, few studies report the successful synthesis of polychromatic CPDs using two or more unconjugated precursors. In this work, we prepare multicolor fluorescent CPDs from a single unconjugated precursor, glucose, via a hydrothermal reaction. By controlling the particle size and degree of graphitization of the synthesized CPDs, their emission wavelength can be tuned in the range 440-625 nm (i.e., almost the entire visible region). Furthermore, the CPDs can be used to construct LEDs of varying colors, including WLEDs (CIE coordinates: 0.34, 0.36) with the correlated color temperature and color rendering index of 4997 K and 92.69, respectively. In brief, the strategy proposed in this study successfully converts unconjugated glucose into high-performance LEDs with great application potential.

37 citations

Journal ArticleDOI
TL;DR: In this paper , a review of advances in sensitizers, including the current status, working mechanisms, design principles, as well as future challenges and endeavor directions, is presented.
Abstract: The attractive features of lanthanide-doped upconversion luminescence (UCL), such as high photostability, nonphotobleaching or photoblinking, and large anti-Stokes shift, have shown great potentials in life science, information technology, and energy materials. Therefore, UCL modulation is highly demanded toward expected emission wavelength, lifetime, and relative intensity in order to satisfy stringent requirements raised from a wide variety of areas. Unfortunately, the majority of efforts have been devoted to either simple codoping of multiple activators or variation of hosts, while very little attention has been paid to the critical role that sensitizers have been playing. In fact, different sensitizers possess different excitation wavelengths and different energy transfer pathways (to different activators), which will lead to different UCL features. Thus, rational design of sensitizers shall provide extra opportunities for UCL tuning, particularly from the excitation side. In this review, we specifically focus on advances in sensitizers, including the current status, working mechanisms, design principles, as well as future challenges and endeavor directions.

20 citations

Journal ArticleDOI
TL;DR: In this article, a novel NIR-II luminescent nanoprobe based on efficient energy transfer from Ce3+ to Er3+ and Nd3+ in sub-10 nm SrS nanocrystals (NCs) was reported.
Abstract: Lanthanide (Ln3+)-doped near infrared (NIR)-II luminescent nanoprobes have shown great promise in many technological fields, but are currently limited by the low absorption efficiency of Ln3+ due to the forbidden 4f→4f transition. Herein, we report a novel NIR-II luminescent nanoprobe based on efficient energy transfer from Ce3+ to Er3+ and Nd3+ in sub-10 nm SrS nanocrystals (NCs), which are excitable by using a commercial blue light-emitting diode (LED). Through sensitization by the allowed 4f→5d transition of Ce3+, the NCs exhibit strong NIR-II luminescence from Er3+ and Nd3+ with quantum yields of 2.9% and 2.3%, respectively. Furthermore, by utilizing the intense NIR-II luminescence of Er3+ from the thermally coupled Stark sublevels of 4I13/2, we demonstrate the application of SrS:Ce3+/Er3+ NCs as blue-LED-excitable NIR-II luminescent nanoprobes for ratiometric thermal sensing. These findings reveal the unique advantages of SrS:Ln3+ NCs in NIR-II luminescence, which may open up a new avenue for exploring novel and versatile luminescent nanoprobes based on Ln3+-doped sulphide NCs.

8 citations

Journal ArticleDOI
TL;DR: In this article, the first nanoparticle synthesis of the mixed-valent ferromagnets Eu3 S4 and EuSm2 S4 was reported, using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine.
Abstract: In targeting reduced valent lanthanide chalcogenides, we report the first nanoparticle synthesis of the mixed-valent ferromagnets Eu3 S4 and EuSm2 S4 . Using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine, we prepared nanoparticles of EuS, Eu3 S4 , EuSm2 S4 , SmS1.9 , and Sm3 S4 . All nanoparticle phases were identified using powder X-ray diffraction, transmission electron microscopy was used to confirm morphology and nanoparticle size, and magnetic susceptibility measurements for determining the ordering temperatures and valence. The UV/Vis, Raman and X-ray photoelectron spectroscopies for each phase were compared. Surprisingly, the phase is influenced by the halide and the reaction temperature, where EuCl2 formed EuS while EuI2 formed Eu3 S4 , highlighting the role of kinetics in phase stabilization. Interestingly, at lower temperatures EuI2 initially forms EuS, and converts over time to Eu3 S4 .

5 citations

Journal ArticleDOI
30 Aug 2021
TL;DR: In this article, the key role of amine surfactants in the controlled anisotropic growth of ZnO nanoparticles that is achieved under mild conditions by organometallic hydrolysis was elucidated.
Abstract: Herein, we elucidate the key role of amine surfactants in the controlled anisotropic growth of ZnO nanoparticles that is achieved under mild conditions by organometallic hydrolysis. The structuring influence of alkyl substituents on the nitrogen atom of amines is jointly analyzed theoretically by DFT modeling, and experimentally by multinuclear NMR (1H, 13C and 17O) spectroscopy. We demonstrate that in initial steps leading to the growth of colloidal ZnO particles, the nature of molecular species that are involved in the solution strongly depends on the structure of the amine surfactant. By using tertiary, secondary or primary amines, no or weak adducts between the amine and zinc, or stable adducts, or adduct oligomers were identified, respectively. Afterwards, following the course of the reaction, the dynamic behavior of the amines on the grown ZnO nanocrystal surfaces is also strongly correlated with their structure. We identified that in the presence of tertiary, secondary or primary amines, no significant [Zn⋯N] adsorption, or surface adsorption with notable surface mobility, or a very strong adsorption is achieved, respectively. The last case, primary amines, significantly involves the structuring of a hydrogen bonding network. Therefore, such surface dynamic behavior has a predominant role in driving the nanocrystal growth, and orienting the ZnO material final morphology. By forming hydrogen bonds at the nanoparticle surface during the growth process, primary amines specifically lead to the formation of nanorods. Conversely, isotropic nanoparticles and aggregates are obtained when secondary and tertiary amines are used, respectively. These findings shed light on the role of weak surface interactions, herein H-bonding, that rule the growth of nano-objects and are as such crucial to identify, study, and control for achieving progress in nanoscience.

4 citations