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Conjugated Polymers Containing BODIPY and Fluorene Units for Sensitive Detection of CN? Ions: Site-Selective Synthesis, Photo-Physical and Electrochemical Properties
摘要： Conjugated polymers containing distinct molecular units are expected to be very interesting because of their unique properties endowed by these units and the formed conjugated polymers. Herein, four new conjugated copolymers based on fluorene and 4,4’-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) have been designed and synthesized via Sonogashira polymerization. The fluorene unit was attached to the 3,5- or 2,6-positions of BODIPY by ethynylenes or p-diacetylenebenzene. The obtained polymers show good thermal stability and broad absorption in the wavelength range from 300 to 750 nm. The effects of site-selective copolymerization and conjugation length along the polymer backbone on the optoelectronic and electrochemical properties of these copolymers were systematically studied by UV-Vis spectroscopy, photoluminescence (PL) and cyclic voltammetry. Besides, it is found that the BODIPY-based copolymers exhibit selectively sensitive responses to cyanide anions, resulting in obvious change of UV-Vis absorption spectra and significant fluorescence quenching of the polymers among various common anions.
关键词： conjugated copolymers,site-selective,cyanide anion,BODIPY
更新于2025-09-23 15:21:01
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Localized Surface Plasmon Resonance-Induced Welding of Gold Nanotriangles and the Local Plasmonic Properties for Multicolor Sensing and Light-Harvesting Applications
摘要： The excitation of localized surface plasmon resonance in gold nanotriangles by continuous light illumination triggered the welding of two adjacent nanotriangles into one nanoparticle. The facing localized surface plasmon resonance generated at the corners of the gold nanotriangles facilitated welding of the nanotriangles, in which electromagnetically seamless bonding was formed. We examined the scanning transmission electron microscopy-electron energy loss spectra of the obtained nanostructure and confirmed the generation of a localized plasmon mode at the bonding spot with an energy of 2.3 eV, which did not appear in the two adjacent gold nanotriangles without bonding. The experimental electron energy loss spectra and maps were supported by the simulation data calculated using the boundary element method. An electromagnetically continuous nanostructure was successfully constructed by a site-selective welding method in this work, resulting in modulation of the localized surface plasmon resonance in nanoparticles, including the localized spots, resonant wavelength and enhancement factor. The generation of a localized surface plasmon resonance mode by welding of nanoparticles can enable multicolor sensing and light harvesting applications.
关键词： plasmon mode,site-selective welding,nanoparticle,electron energy loss spectroscopy,localized surface plasmon resonance,gold nanotriangle
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Ultrafast Dynamics in Quantum Dot Doped Nanocomposites at Low Temperatures: Study by Means of Site-Selective Spectroscopy
摘要： Study of the dynamics and luminescence properties of nanocomposite materials based on semiconductor quantum dots is an important and urgent trend of modern physics and materials science. Semiconductor quantum dots have a number of unusual photophysical and spectral properties, which are determined by their structure, size and microscopic features of interaction with the local environment. Considerable efforts are aimed to search for and study new luminescence labels [1] and suitable matrices for functional quantum-dot-based materials, e.g., liquid crystals [2]. In this paper we discuss the new data on ultrafast dynamics in nanocomposites doped with semiconductor colloidal nanocrystals (quantum dots, QDs) revealed by two types of site-selective spectroscopy techniques. Optical dephasing in a thin film of double-coated CdSe/CdS/ZnS QDs was studied in a wide range of cryogenic temperatures using a method of the photon echo. Experiments were performed using unique incoherent photon echo spectrometer (see e.g. [3]). We measured the decay curves of 2-pulse incoherent photon echo signals in ensemble of QDs and obtained very short relaxation times (about hundreds of femtoseconds) in a temperature range from 4.5 K to 50 K [4]. These results are extremely different from the data obtained in the ensembles of impurity organic dye molecules for which the relaxation times are about nanoseconds at this very temperature. Possible reasons for such ultrafast optical dephasing can be associated: (1) with structural inhomogeneities of QDs themselves; (2) with the features of internal dynamics of the emitting core (e.g., blinking of QDs); (3) with the surface states in a QDs shells. Furthermore, the size variance and strongly inhomogeneous local environment (local fields in a solid matrix) can lead to fast relaxation in the QDs ensemble. In order to separate the contributions to the optical dephasing of the processes of interaction of quantum dots with the matrix from the processes inside the QDs themselves, we measured the temperature dependences of the luminescence spectra of nanocomposites. Generally, with the temperature decrease, the maxima of the exciton bands in a luminescence spectra shift to the UV spectral range. Such phenomenon can be described taking into account the electron-phonon (exciton-phonon) interaction. The temperature shift of the exciton luminescence spectrum can be described using the modified Varshni equation [5]. Theoretical model that takes into account the electron-phonon interaction made it possible to quantitatively describe the temperature dependences of the exciton luminescence spectra of QDs, as well as to determine the values of the Huang-Rhys factor and the average energy of phonons in nanocrystals. In our experiments no noticeable temperature changes in the exciton maxima widths have been observed, which is related, on the one hand, to the resolution of used experimental technique and, on the other hand, to the occurrence of significant inhomogeneous broadening of the spectra caused by a large dispersion of QD sizes. Describing the temperature behavior of the position and width of the luminescence spectra of QDs one should take into account an interaction of the electronic transition of the impurity with vibrational excitations, e.g. with local or quasi-local phonons in a solid matrix. In this connection, we have studied the influence of the matrix on luminescence properties of QD-doped nanocomposites. The combination of the photon echo and luminescence spectroscopy is a powerful method to study the ultrafast processes of interaction of the impurity ensemble of QDs with a solid matrix as well as the intrinsic dynamics of quantum dots themselves.
关键词： ultrafast dynamics,luminescence,quantum dots,photon echo,nanocomposites,site-selective spectroscopy
更新于2025-09-11 14:15:04
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Site‐Selective and van der Waals Epitaxial Growth of Rhenium Disulfide on Graphene
摘要： The surface property of growth substrate imposes significant influence in the growth behaviors of 2D materials. Rhenium disulfide (ReS2) is a new family of 2D transition metal dichalcogenides with unique distorted 1T crystal structure and thickness-independent direct bandgap. The role of growth substrate is more critical for ReS2 owing to its weak interlayer coupling property, which leads to preferred growth along the out-of-plane direction while suppressing the uniform in-plane growth. Herein, graphene is introduced as the growth substrate for ReS2 and the synthesis of graphene/ReS2 vertical heterostructure is demonstrated via chemical vapor deposition. Compared with the rough surface of SiO2/Si substrate with dangling bonds which hinders the uniform growth of ReS2, the inert and smooth surface nature of graphene sheet provides a lower energy barrier for migration of the adatoms, thereby promoting the growth of ReS2 on the graphene surface along the in-plane direction. Furthermore, patterning of the graphene/ReS2 heterostructure is achieved by the selective growth of ReS2, which is attributed to the strong binding energy between sulfur atoms and graphene surface. The fundamental studies in the role of graphene as the growth template in the formation of van der Waals heterostructures provide better insights into the synthesis of 2D heterostructures.
关键词： rhenium disulfide,chemical vapor deposition,2D heterostructures,graphene,site-selective growth
更新于2025-09-04 15:30:14