Effect of shell thickness on two-photon absorption and refraction of colloidal CdSe/CdS core/shell nanocrystals

Zhu, Baohua; Zhang, Huichao; Zhang, Zong-Yan; Cui, Yiping; Zhang, Jiayu

doi:10.1063/1.3665400

Cited by 44 publications

(36 citation statements)

References 21 publications

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“…Since the core has a higher local field enhancement compared to the shell, this leads to an overall reduction in the nonlinearity of the nanoparticles with thicker shells. Note that, similar nonmonotonic size dependent enhancement of ultrafast optical nonlinearity (fs or ps pulse excitations) has been previously reported in CdSe/CdS colloidal core/shell nanocrystals, Mn‐doped ZnSe nanocrystals, and Au‐SiO 2 core/shell nanoparticles . However, in contrast to quantum dots and noble metals, ferrite nanoparticles are environmentally friendly, inexpensive, and very stable with temperature or in reactive environments.…”

Section: Resultssupporting

confidence: 73%

“…The nonlinear susceptibility increases up to a shell thickness of 2 nm, and slightly decreases thereafter. The measured values show a slight deviation from the theoretical curve for samples with thicker shells, which might be due to the presence of nonradiative surface traps formed due to the strain and lattice mismatch at the core/shell interface …”

Section: Resultsmentioning

confidence: 78%

“…For Co1 seed and Mn1 seed, χ m (3) is calculated to be 2.4 × 10 −21 m 2 V −2 and 1.96 × 10 −21 m 2 V −2 , respectively. Now, according to the local field theory, the effective nonlinear susceptibility of the core/shell system dispersed in a dielectric medium (toluene in the present case) is given by

χ_{eff}^{(3)} = P {(3 ε_{0} normal/ (2 ε_{0} + ε_{eff}))}^{4} χ_{normalm}^{(3)}

where P is the volume fraction of nanoclusters in the dispersion, and (3ε 0 /(2ε 0 + ε eff )) 4 is the local field enhancement factor. ε eff is given by ε 0 + 3ε 0 Pb, where b = (ε 2 − ε 0 + (ε 0 + 2ε 2 )ρ 1 f 3 )/(ε 2 + 2ε 0 + 2(ε 2 −ε 0 )ρ 1 f 3 ), with ρ 1 = (ε 1 − ε 2 )/(ε 1 + 2ε 2 ); f is the ratio between the radii of core ( r 1 ) and core/shell ( r 2 ); and ε 0 , ε 1 , and ε 2 are the dielectric constants of the dielectric, core material, and the shell material, respectively.…”

Section: Resultsmentioning

confidence: 99%

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Enhanced Ultrafast Nonlinear Optical Response in Ferrite Core/Shell Nanostructures with Excellent Optical Limiting Performance

Perumbilavil

López‐Ortega

Tiwari

et al. 2018

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Nonlinear optical nanostructured materials are gaining increased interest as optical limiters for various applications, although many of them suffer from reduced efficiencies at high-light fluences due to photoinduced deterioration. The nonlinear optical properties of ferrite core/shell nanoparticles showing their robustness for ultrafast optical limiting applications are reported. At 100 fs ultrashort laser pulses the effective two-photon absorption (2PA) coefficient shows a nonmonotonic dependence on the shell thickness, with a maximum value obtained for thin shells. In view of the local electric field confinement, this indicates that core/shell is an advantageous morphology to improve the nonlinear optical parameters, exhibiting excellent optical limiting performance with effective 2PA coefficients in the range of 10 cm W (100 fs excitation), and optical limiting threshold fluences in the range of 1.7 J cm . These values are comparable to or better than most of the recently reported optical limiting materials. The quality of the open aperture Z-scan data recorded from repeat measurements at intensities as high as 35 TW cm , indicates their considerably high optical damage thresholds in a toluene dispersion, ensuring their robustness in practical applications. Thus, the high photostability combined with the remarkable nonlinear optical properties makes these nanoparticles excellent candidates for ultrafast optical limiting applications.

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Section: Resultssupporting

confidence: 73%

Section: Resultsmentioning

confidence: 78%

χ_{eff}^{(3)} = P {(3 ε_{0} normal/ (2 ε_{0} + ε_{eff}))}^{4} χ_{normalm}^{(3)}

Section: Resultsmentioning

confidence: 99%

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Enhanced Ultrafast Nonlinear Optical Response in Ferrite Core/Shell Nanostructures with Excellent Optical Limiting Performance

Perumbilavil

López‐Ortega

Tiwari

et al. 2018

Small

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“…57) could also induce intrinsic piezoelectric polarization charges at the core–shell interface that result in an internal electric field. This indicates that the photoinduced screening of the internal field by the photoexcited electron–hole pairs could be another possible origin for the enhanced σ n in MAPbBr 3 /(OA) 2 PbBr 4 NCs3436. Furthermore, the dielectric confinement (local field effect) resulting from the relatively large difference between the dielectric constants of the core MAPbBr 3 (ref.…”

Section: Discussionmentioning

confidence: 99%

Giant five-photon absorption from multidimensional core-shell halide perovskite colloidal nanocrystals

Chen

Bhaumik²,

Veldhuis³

et al. 2017

Nat Commun

193

280

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Multiphoton absorption processes enable many technologically important applications, such as in vivo imaging, photodynamic therapy and optical limiting, and so on. Specifically, higher-order nonlinear absorption such as five-photon absorption offers significant advantages of greater spatial confinement, increased penetration depth, reduced autofluorescence, enhanced sensitivity and improved resolution over lower orders in bioimaging. Organic chromophores and conventional semiconductor nanocrystals are leaders in two-/three-photon absorption applications, but face considerable challenges from their small five-photon action cross-sections. Herein, we reveal that the family of halide perovskite colloidal nanocrystals transcend these constraints with highly efficient five-photon-excited upconversion fluorescence—unprecedented for semiconductor nanocrystals. Amazingly, their multidimensional type I (both conduction and valence band edges of core lie within bandgap of shell) core–shell (three-dimensional methylammonium lead bromide/two-dimensional octylammonium lead bromide) perovskite nanocrystals exhibit five-photon action cross-sections that are at least 9 orders larger than state-of-the-art specially designed organic molecules. Importantly, this family of halide perovskite nanocrystals may enable fresh approaches for next-generation multiphoton imaging applications.

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“…At low intensity such as 6.6 GW·cm −2 , NCs exhibited SA. As the intensity increased to 8.5 GW·cm −2 , 9.4 GW·cm −2 , 15.1 GW·cm −2 , 17.9 GW·cm −2 , 18.9 GW·cm −2 and 20.8 GW·cm −2 , a valley appeared in the peak at the focus and was getting deeper with incident intensity increased, which meaned that there was CT between them in two components [34]. The peak-to-valley development of OA Z-scan curves at different input intensities could further demonstrate the CT evolution in graphene-γMnS.…”

Section: Nlo Property Of Ncsmentioning

confidence: 96%

Facile One-Step Synthesis and Enhanced Optical Nonlinearity of Graphene-γMnS

Zhang

et al. 2019

Nanomaterials

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Graphene-γMnS were prepared by facile one-step hydrothermal method. Structures and properties of samples were explored by characterization, and nonlinear optical (NLO) enhancement of nanocomposites (NCs) was fully studied. Nanoparticles and NCs were tested at 532 nm by a Z-scan technique. With γMnS attached in G layers, NLO susceptibility of graphene-γMnS was greatly improved under single-pulse laser irradiation compared with G and γMnS. The nonlinearity enhanced was attributed to local field effect and charge transfer between γMnS and graphene layers. And NLO property enhancement was restricted by non-radiative defects in graphene-γMnS. Exploring the mechanism of nonlinearity enhancement was significant for fabrication of NLO devices. However, the optical nonlinearity decreased first and then increased with further increased addition of GO, because the dispersion of γMnS attached on graphene surface might make density of sp 2 fragment and defects changed. Graphene-γMnS exhibited excellent and tunable NLO performance, illustrating that NCs materials have potential applications in NLO devices. Nanomaterials 2019, 9, 1654 2 of 16 and graphene [12][13][14]. However, there are few reports about NLO performance of graphene-γMnS. In fact, we have previously studied αMnS/rGO without thoroughly investigating the nonlinearity of graphene-γMnS and the mechanism of NLO performance enhanced of NCs [15]. It is necessary to explore NLO responses of graphene-γMnS and its mechanism of enhanced nonlinearity.In this study, graphene-γMnS was synthesized by facile one-step hydrothermal method, and mechanism of NLO enhancement was discussed. Nonlinearity of NCs was controlled by changing amount of GO added, and samples were tested at 532 nm by picosecond (PS) laser pulse. We want to explore whether graphene-γMnS had potential applications in optical communication, optical limiter, and all-optical switch. Experiments Synthesis of Graphene Oxide ( GO) and Graphene-γMnSGO was prepared by improved Hummer method [16]. Firstly, graphite powder was oxidized to GO by KMnO 4 and 98% H 2 SO 4 . Then, a solution was mixed with H 2 O 2 and the mixture was washed several times with deionized water to remove impurities. Finally, products were dried at 45 • C for 48 h in vacuum drying oven. Improved Hammer method increased generation efficiency and oxidation degree of GO. Furthermore, this method could effectively prevent generation of toxic gases which caused harm to human body. High efficiency, high quality, and no toxicity in GO synthesis were important for large-scale production of GO.Graphene-γMnS was prepared by facile one-step hydrothermal method. The synthesis process of NCs was shown in Figure 1. Firstly, GO was dispersed in ethylene glycol. Secondly, TAA and MnCl 2 ·4H 2 O were added to GO suspension. After half-an-hour stirring, the solution was transferred to Teflon-lined stainless-steel autoclave and reacted at 170 • C for 6 h. The reaction temperature in our previous study was 190 • C and product was different [15]. Then, products wer...

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Effect of shell thickness on two-photon absorption and refraction of colloidal CdSe/CdS core/shell nanocrystals

Cited by 44 publications

References 21 publications

Enhanced Ultrafast Nonlinear Optical Response in Ferrite Core/Shell Nanostructures with Excellent Optical Limiting Performance

Enhanced Ultrafast Nonlinear Optical Response in Ferrite Core/Shell Nanostructures with Excellent Optical Limiting Performance

Giant five-photon absorption from multidimensional core-shell halide perovskite colloidal nanocrystals

Facile One-Step Synthesis and Enhanced Optical Nonlinearity of Graphene-γMnS

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