Linear and Nonlinear Optical Properties of CdS and CdSe Nanoparticles   Stabilized with Poly(N-vinyl-2-pyrrolidone)

The variation of CdSe nanoparticle size as a function of synthesis conditions is presented. Cadmium sulphate (CdSO 4 ), cadmium chloride (CdCl 2 ) and sodium selenosulphate (Na 2 SeSO 3 ) solutions were used as precursors. Nanoparticles were synthesized by aqueous chemical methods. The synthesis parameters studied were pH, Cd:Se ratio and the type of stabilizing agent. Three different stabilizing agents were used, thioglycolic acid, mercaptoethanol and poly(vinyl pyrrolidone). Fourier transform infrared spectroscopy results confirmed the presence of the stabilizing agent on the surface of the nanoparticles. Ultraviolet visible and X-ray powder diffraction measurements were used to estimate the trend of size variations of the particles with different synthesis parameters, which agreed fairly by both techniques and the crystal structure. Additionally, the size of the nanoparticles was obtained by transmission electron microscopy measurements. Whilst the effect of pH was different for each of the different stabilizing agents due to the different chemical groups in the thiol compounds and the size of the nanoparticles varied with the used stabilizing agents, the effect of Cd:Se ratio in the size of nanoparticles showed the same tendency for the several stabilizing agents.

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“…. This width variation is due to adsorption of CdSe NP on the surface of PVP which prevents the self association of lactam [29].…”

Section: Ftir Spectroscopymentioning

confidence: 99%

Effect of different aqueous synthesis parameters on the size of CdSe nanocrystals

et al. 2012

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“…The investigations on the nonlinear optical properties of semiconductor nanocrystals have focused mainly into the thirdorder optical nonlinearity (or second hyperpolarizability γ). 1,2,[9][10][11][12][13][14][15][16][17][18][19] A large enhancement of this optical nonlinearity because of size quantization of the exciton motion has been predicted by Nakamura et al 9 and by Banyai et al 10 Although some * To whom correspondence should be addressed. E-mail: dvp@ npd.ufpe.br.…”

Section: Introductionmentioning

confidence: 99%

Size and Band-Gap Dependences of the First Hyperpolarizability of Cd_xZn₁_-_xS Nanocrystals

et al. 2002

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The first hyperpolarizability of aqueous suspensions of polyphosphate stabilized CdS nanocrystals of different mean sizes and of Cd x Zn1 - x S nanocrystals (x = 0, 0.25, 0.75, 1) was determined by the hyper-Rayleigh scattering technique. We report the first experimental observation that the first hyperpolarizability decreases as the band gap energy increases. This is ascribed to the decrease of the resonance enhancement. The surface modification of 9 nm CdS nanocrystals with OH- increases the first hyperpolarizability by a factor 1.7. This is explained in terms of the higher polarizability of the surface terminating groups after the OH- modification. Finally, we have also established the size dependence of the first hyperpolarizability for CdS nanocrystals. Although it increases with the particle size, its values normalized per CdS pair increase with decreasing of size, leading to an enhancement by 1 order of magnitude for 2 nm particles in comparison with bulk. This is explained by assuming the enhancement of both the bulk contribution from the noncentrosymmetric nanocrystal core and the surface contribution. The enhancement of the bulk contribution is ascribed to quantum confinement effects on the normalized oscillator strengths. The surface contribution becomes more relevant as the size decreases and may be enhanced by several effects, especially surface polarization. A two-level model can explain both the band-gap and the size dependences.

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“…This leads to more absorption of electrons from the trap levels to the conduction bands [23]. Mathew et al [24] has also reported that the involvement of deep trap state level is the source of free-carriers in core/shell nanomaterials.…”

Section: Page 11 Of 24mentioning

confidence: 99%

Two photon absorption studies of PVA coated CdSe/ZnSe and CdSe/CdS core/shell nanostructures

Sharma

Tripathi

2015

Chemical Physics Letters

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Linear and Nonlinear Optical Properties of CdS and CdSe Nanoparticles Stabilized with Poly(N-vinyl-2-pyrrolidone)

Cited by 42 publications

References 22 publications

Effect of different aqueous synthesis parameters on the size of CdSe nanocrystals

Effect of different aqueous synthesis parameters on the size of CdSe nanocrystals

Size and Band-Gap Dependences of the First Hyperpolarizability of Cd_xZn₁_-_xS Nanocrystals

Two photon absorption studies of PVA coated CdSe/ZnSe and CdSe/CdS core/shell nanostructures

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Linear and Nonlinear Optical Properties of CdS and CdSe Nanoparticles Stabilized with Poly(N-vinyl-2-pyrrolidone)

Cited by 42 publications

References 22 publications

Effect of different aqueous synthesis parameters on the size of CdSe nanocrystals

Effect of different aqueous synthesis parameters on the size of CdSe nanocrystals

Size and Band-Gap Dependences of the First Hyperpolarizability of CdxZn1-xS Nanocrystals

Two photon absorption studies of PVA coated CdSe/ZnSe and CdSe/CdS core/shell nanostructures

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Size and Band-Gap Dependences of the First Hyperpolarizability of Cd_xZn₁_-_xS Nanocrystals