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Preserved two-photon optical properties of hydrophilic proteins-conjugated quantum dots
摘要： Nonlinear optical properties of colloidal CdSe quantum dots conjugated with proteins were investigated in a wide spectral range with the two-photon excited emission technique using a tunable femtosecond laser system in the range from 700 to 1000 nm. The most signi?cant value of the two-photon absorption cross section σ2 for 2.9 nm size hydrophilic CdSe quantum dot was equal to 4 505 GM, while the two-photon excitation action cross section σ2·QY was found to be 0.101 GM at 900 nm. The nonlinear absorption properties are present as appropriate cross sections normalized per molecular weight which allows comparison of the nonlinear properties of the studied quantum dots with various nanosystems or organic dyes. The properties of these proteins covering hydrophilic colloidal quantum dots can be potentially useful for nonlinear bioimaging.
关键词： Hydrophilization,Semiconducting quantum dots,Nonlinear optical properties,Nanophotonics,Proteins
更新于2025-11-20 15:33:11
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Effect of different hardness and melting point of the metallic surfaces on structural and optical properties of synthesized nanoparticles
摘要： The relations between macroscopic and microscopic characteristics of materials are of utmost importance for synthesis of multi-atomic structures with advanced properties. We analyze the influence of pulse duration, pulse energy and temperature of liquid on the process of formation of nanoparticles (NPs) of the metals (In, Sn, Zn and W) with different hardness and melting temperature by laser ablation in liquid environment. Composition, morphology dynamics and properties of nanoparticle suspensions are studied using TEM analysis and Z-scan technique. The nonlinear optical properties of NPs are analyzed at 800 and 400 nm using 60 fs and 200 ps pulses. We show that the temperature of liquid environment influences the formation of NPs and their nonlinear optical properties. In addition, pulse energy have little influence on the formation, morphology and size of NPs during ablation of low hardness and melting point metal (In). However, pulse duration plays a very important role during the formation of NPs, especially the ultra-short pulse has a positive effect on the preparation of NPs with smaller particle size.
关键词： nonlinear optical properties,metal nanoparticles,laser ablation in liquid
更新于2025-09-23 15:23:52
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Linear and non linear optical properties of Sb2Se3 thin films elaborated from nano-crystalline mechanically alloyed powder
摘要： Sb2Se3 powder is achieved by mechanical milling of Sb and Se elements. X-ray diffraction analysis indicated the formation of Sb2Se3 orthorhombic phase. The latter finding is confirmed by both X-ray photoelectron spectroscopy characterization and Raman spectroscopy. Magnetic measurement revealed the ferromagnetic character of Sb2Se3 powder. Thin films were obtained by thermal deposition using Sb2Se3 powder as a precursor. Optical measurements carried out on thin films showed a high absorption coefficient and a direct band gap of 1.61 eV. The material has then potential application in photovoltaic conversion. Thin film refractive index dispersion (n) obeys Cauchy dispersion equation. n is investigated and found to comply with Wemple–DiDomenico single oscillator dispersion model. The energy E0 of the oscillator and Ed dispersion energy are derived from the refractive index investigation. Spitzer–Fan model exploitation was allowed to derive the high-frequency dielectric constant ε∞ and the carrier density N/m* ratio. Additionally, Verdet constant V is determined based on the refractive index dispersion study. Furthermore, the nonlinear susceptibility χ(3) as well as nonlinear refractive index are determined for Sb2Se3 thin films. The nanostructure of the material is likely responsible not only for the high nonlinear characteristics but also for the low magnetic character in Sb2Se3.
关键词： Nonlinear optical properties,Optical properties,Thermal deposition,Sb2Se3,Mechanical milling
更新于2025-09-23 15:21:21
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Preparation of composite Ag@Au core–shell nanoparticles and their linear and nonlinear optical properties
摘要： We herein report the preparation of composite Ag@Au core–shell nanoparticles (NPs) through galvanic replacement reaction and the investigations of linear and nonlinear optical properties. TEM micrographs envisage the formation of core–shell NPs. EDS elemental mapping images demonstrate the homogeneous distribution of the elements and their chemical composition. The powder XRD pattern confirms the formation of highly crystalline composite Ag@Au core–shell NPs. The UV–Vis absorption spectrum shows contribution of Ag and Au characteristic absorption bands and the slight red shift provides the strong evidence for coating of Au shell over the Ag core. Moreover, the linear optical parameters such as the extinction coefficient, reflectance, refractive index, conductivity, susceptibility and polarizability are studied. z-scan analysis reveals the enhanced nonlinear optical properties of the composite Ag@Au core–shell NPs with nonlinear refraction coefficient (n2) being ten times higher than that of Ag NPs and eight times increase in comparison with that of Au NPs.
关键词： Nonlinear optical properties,Ag@Au core–shell nanoparticles,z-scan technique,Galvanic replacement reaction,Linear optical properties
更新于2025-09-23 15:21:21
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Quantum dots of two-dimensional Ruddlesdena??Popper organica??inorganic hybrid perovskite with high optical limiting properties
摘要： Hybrid perovskites have been investigated for various potential applications because of their tunable optical properties. In this paper, we report the synthesis of quantum dots (QDs) of two-dimensional (2D) Ruddlesden–Popper (RP) hybrid perovskite using a top-down approach. The QDs of the developed 2D RP perovskite exhibit high and sharp photoluminescence in the ultraviolet region. The sharp peak in the absorption spectrum and the intense photoluminescence in the ultraviolet region indicate strong quantum confinement in these particles, which is further confirmed by x-ray photoelectron spectroscopy. These QDs show superior nonlinear optical scattering and absorption properties with the optical z-scan technique and strong nonlinear absorption property with the photoacoustic z-scan technique. Evaluating the nonlinear optical properties using two complementary techniques provides a deeper understanding of the nonlinear mechanism involved in the optical limiting process. The two-photon absorption coefficient obtained by optical z-scan is 7.2 × 102 cm/GW, which is larger than that of most perovskite nanocrystals and nanosheets. Our studies, therefore, reveal a new class of material, 2D RP perovskite QDs, which show important nonlinear properties that are important for optical limiting applications.
关键词： Ruddlesden–Popper perovskite,optical limiting,nonlinear optical properties,Quantum dots,two-photon absorption
更新于2025-09-23 15:21:01
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The laser field controlling on the nonlinear optical specifications of the electric field-triggered Rosen-Morse quantum well
摘要： We consider, for the first time, optical specifications such as the nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG) of quantum well (QW) that has the Rosen-Morse potential confinement and is generated by GaAs/GaAlAs heterostructure. To do this, QW structure is firstly asymmetrized by applying an external electric field, as 10 kV/cm. Therefore, the electric field-triggered (F = 10 kV/cm) Rosen-Morse QW (eftRMQW) is taken into consideration throughout the study. In this study, it is elucidated that how to control NOR, SHG and THG optical responses through monochromatic linearly polarized intense laser field (ILF). In order to be able to investigate the ILF effects, the time-dependent of ILF is removed to potential energy term of the wave equation by using Kramers-Henneberger (KH) and the dipole approximations, building the laser-dressed potential. Then, the bound state energies and the wave functions of eftRMQW are obtained using the diagonalization method within the effective mass approach and the parabolic approximation. The influences of the ILF and structural parameters of eftRMQW on NOR, SHG and THG coefficients are discussed in detail. The optimum of structure is ferreted out for devices design and applications that will consider eftRMQW, and for this optimum the alternative parameter analysis is carried out.
关键词： Nonlinear optical properties,Laser field,Electric field,Rosen-Morse quantum well
更新于2025-09-23 15:21:01
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Passively Q-switched laser with specific chiral SWCNTs selected by N-CS as saturable absorber at
摘要： The single-wall carbon nanotubes (SWCNTs) with the specific chirality (6, 5) and (7, 5) were sorted out by the density gradient ultracentrifugation (DGU) method. 2D photoluminescence excitation–emission map and the Raman spectrum confirmed the successful chirality-selection. The nonlinear optical performance of the chirality-selected SWCNTs was investigated by an open-aperture Z-scan setup. By employing the prepared SWCNTs saturable absorber (SWCNTs-SA), the minimum pulse duration of 115 ns with a pulse repetition rate of 550 kHz was obtained in the passively Q-switched (PQS) laser operation.
关键词： Q-switching,Chirality selection,Nonlinear optical properties,SWCNTs
更新于2025-09-23 15:21:01
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Enhanced nonlinear optical behavior of graphene-CuO nanocomposites investigated by Z-scan technique
摘要： Graphene-CuO nanocomposites were synthesized by the solvothermal method, and graphene (G) were prepared for comparison. The morphologies and structures of samples were investigated by x-ray diffraction, scanning electron microscopy, Raman spectroscopy and ultraviolet-visible absorption spectroscopy. The nonlinear optical (NLO) properties were tested by the Z-scan technology with 1030 nm laser pulses (340 fs, 1000 Hz). The analyse demonstrates that the NLO properties of the graphene-CuO nanocomposites are significantly enhanced compared with graphene, the doping of CuO increases the time of the electron transfer and the photon transition, suppress the recombination between electrons and holes, and prolong the working time of the free carrier, ultimately enhance the nonlinear optical properties of nanocomposites. The results provide a facile approach of doping CuO in graphene to obtain nanocomposites with excellent NLO properties, and the nanocomposites exhibited potential applications in optical devices such as optical switch and optical sensors, etc.
关键词： Nonlinear optical properties,Z-scan technology,Nanocomposites
更新于2025-09-23 15:21:01
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Magnetoa??optical specifications of Rosena??Morse quantum dot with screw dislocation
摘要： This is the first study to consider a quantum dot with screw dislocation that has Rosen-Morse (RM) confinement potential, generated by a GaAs/GaAlAs heterostructure. An external magnetic field and Aharonov-Bohm (AB) flux field were also applied on RM quantum dot (RMQD) in order to stave the effects of a screw dislocation defect. The combined effect of the screw dislocation defect, the external magnetic field, and AB flux field on the total refractive index changes (TRICs) and the total absorption coefficients (TACs) of RMQD are thus investigated. Cylindrical coordinates are used due to the direction of application of the torsion and the external fields, as well as due to the structure's symmetry. The effective mass approximation and tridiagonal matrix methods are used in order to obtain the subband energy spectra and electronic wave functions of RMQD. The nonlinear optical specifications of RMQD are checked using compact-density-matrix formalism within the framework of the iterative method. Reviews without screw dislocation are also carried out in order to be able to clarify the effects of a screw dislocation defect on the optical properties, and then, both cases are deliberated. This study is the first attempt to analyze the AB flux field for RMQD without screw dislocation. In the present study, the influences of a screw dislocation defect on RMQD's TRICs and TACs are probed by considering different values of the external magnetic field and AB flux field, and the ranges of corresponding parameters on the optimum of the structure are specified. Moreover, the study also elucidates how to rule out the effects of screw dislocation on optical specifications by means of the external fields. Despite a certain screw dislocation, the frequency range is determined where the structure behaves as if it is perfect (namely, without screw dislocation) for its optimum, which in turn is crucial for experimental applications.
关键词： quantum dot,magnetic field,screw dislocation,Aharonov-Bohm flux field,nonlinear optical properties
更新于2025-09-23 15:19:57
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Spectral analysis combined with nonlinear optical measurement of laser printed biopolymer composites comprising chitosan/SWCNT
摘要： Biopolymer composites based on two types of chitosan (chitosan succinate and low-molecular weight chitosan) with single-walled carbon nanotubes (SWCNT) were created by laser printing. SWCNT have good dispersibility in chitosan solutions and therefore, can form relatively homogeneous films that was shown in scanning electron microscopy images. For the studies film composites were formed under the action of laser radiation on aqueous dispersion media. Study of the nonlinear optical process during the interaction of laser radiation with a disperse media has shown that low-molecular chitosan has a large nonlinear absorption coefficient of 17 cm/GW, while the addition of SWCNT lead to a significant increase up to 902 cm/GW. The threshold intensity for these samples was 5.5 MW/cm2 with nanotubes. If intensity exceeds the threshold value, nonlinear effects occur, which, in turn, lead to the transformation of a liquid into a solid phase. Characterization of films by FTIR and Raman spectroscopy indicated arising molecular interactions between chitosan and SWCNT detected as a small frequency shift and a change in the shape of radial breathing mode (RBM). The results indicate the possibility using aqueous dispersion media based on chitosan and SWCNT to create three-dimensional films and scaffolds for tissue engineering by laser printing.
关键词： Tissue engineering,Carbon nanotubes,Nonlinear optical properties,Chitosan,Spectroscopy
更新于2025-09-23 15:19:57