Determination of optical constants of molecular films assembled via alternate polyion adsorption

Ramsden, Jeremy J.; Lvov, Y.; Decher, Gero

doi:10.1016/0040-6090(94)06262-j

Cited by 138 publications

(125 citation statements)

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“…Cationic polyelectrolyte (PE) was deposited on all three surfaces using the same selflimiting procedure. 57 Substrates were immersed in a 0.003 mols of monomer/L solution of poly(allylamine) hydrochloride (PAH)/1 M NaCl for 30 min, immersed in DI water for 1 min, rinsed with DI water, and dried under high purity nitrogen. A 100 L drop of diluted functionalized gold particle solution (ϳ10 Ϫ11 M) was placed on the PE surface of each surface for 1 min, rinsed with DI water, and dried with nitrogen.…”

Section: Methodsmentioning

confidence: 99%

Gold Nanoparticles on Polarizable Surfaces as Raman Scattering Antennas

et al. 2010

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Surface plasmons supported by metal nanoparticles are perturbed by coupling to a surface that is polarizable. Coupling results in enhancement of near fields and may increase the scattering efficiency of radiative modes. In this study, we investigate the Rayleigh and Raman scattering properties of gold nanoparticles functionalized with cyanine deposited on silicon and quartz wafers and on gold thin films. Dark-field scattering images display red shifting of the gold nanoparticle plasmon resonance and doughnut-shaped scattering patterns when particles are deposited on silicon or on a gold film. The imaged radiation patterns and individual particle spectra reveal that the polarizable substrates control both the orientation and brightness of the radiative modes. Comparison with simulation indicates that, in a particle−surface system with a fixed junction width, plasmon band shifts are controlled quantitatively by the permittivity of the wafer or the film. Surface-enhanced resonance Raman scattering (SERRS) spectra and images are collected from cyanine on particles on gold films. SERRS images of the particles on gold films are doughnut-shaped as are their Rayleigh images, indicating that the SERRS is controlled by the polarization of plasmons in the antenna nanostructures. Near-field enhancement and radiative efficiency of the antenna are sufficient to enable Raman scattering cyanines to function as gap field probes. Through collective interpretation of individual particle Rayleigh spectra and spectral simulations, the geometric basis for small observed variations in the wavelength and intensity of plasmon resonant scattering from individual antenna on the three surfaces is explained.

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Section: Methodsmentioning

confidence: 99%

Gold Nanoparticles on Polarizable Surfaces as Raman Scattering Antennas

et al. 2010

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“…The PDDA is expected to be adsorbed in loops, engendering a columnar structure with positive birefringence. 7,26 Hence, the average refractive index of the first PDDA layer calculated by assuming an isotropic film severely underestimates the real value. 9 When the CdTe nanoparticles flow over the substrate (starting at c 1 ), film refractive index increases to a sharp peak, while the thickness of the film remains unchanged, and during the increase of n A , the total mass deposited (tracked as optical path or N TM ) shows a small linear increase with time.…”

Section: Labelmentioning

confidence: 99%

“…The following rapid decrease of apparent average refractive index while the strongly refracting CdTe particles continue to be added to the system makes no sense unless n A is being progressively underestimated due to increasingly positive birefringence, 9,15 which, in turn, is due to a predominantly columnar molecular orientation, which has been established as a characteristic feature of polymer polyelectrolyte-only APED. 26 In conclusion, OWLS reveals itself as a very useful in situ technique for yielding fine kinetic structural information about the deposition, well satisfying the need for critical scrutiny of the assembly process. Careful analysis of this information revealed that the addition of the nanoparticles to the polymer polyelectrolyte is a two-stage process: initially, the particles enter nanopores in the polymer layer and this stage strictly precedes the formation of a nanoparticle-rich adlayer.…”

Section: Labelmentioning

confidence: 99%

“…5 confirms that the polycationic PDDA (flow initiated at b) forms an initial layer on the negatively charged Si 0.6 Ti 0.4 O 2 , 25 as expected. 26 The slight decrease when water flowed (arrow a 2 ) is presumably due to the removal of weakly entangled polymer chains. The PDDA is expected to be adsorbed in loops, engendering a columnar structure with positive birefringence.…”

Section: Labelmentioning

confidence: 99%

“…Growth is clearly linear as previously observed for APED involving only linear organic polymer polyelectrolytes. 26 We can therefore exclude the "exponential" growth mechanism, 16 which has been observed under certain conditions of APED. Similarly, plotting d A vs layer number (not shown) yields a per-layer thickness of 3 nm, which confirms the analysis of device cross-section carried out by Bertoni et al, 2 and which corresponds to the mean diameter of the nanoparticles.…”

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confidence: 99%

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Apparent self-accelerating alternating assembly of semiconductor nanoparticles and polymers

Horváth

Gardner

Ramsden

2015

Applied Physics Letters

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Alternating polyelectrolyte deposition is a promising route to the low-cost fabrication of electroluminescent devices based on semiconductor nanoparticles, but optimization and exploitation demand a deeper understanding of the fabrication mechanism, which has not hitherto been scrutinized in detail. Nanoparticle–polymer composites were assembled by repeated alternate exposures of a substrate to polyanionic thioglycolate-coated CdTe nanoparticles and the organic polycation polydiallyldimethylammonium while monitoring the process kinetics in situ using optical waveguide lightmode spectroscopy, which enabled detailed structural information to be obtained with good time resolution. This complements the previously reported device characterization. Two hitherto unnoticed features were observed: (i) apparently spontaneous acceleration of addition of semiconductor nanoparticles after a certain quantity has already been deposited and (ii) during subsequent exposure to the organic polycation, an appreciable proportion of the immediately previously deposited nanoparticles is removed. Analysis of the evolution of the optogeometrical parameters of the assembly revealed that during the initial slow addition the nanoparticles enter nanopores in the immediately previously deposited polymer. The deposition régime then switches abruptly to the formation of an adlayer of the nanoparticles. These are initially deposited in considerable excess, which is removable by simple dilution of the system. Further nanoparticle removal takes place during the following phase of polycation deposition via a process of particle scavenging by the polycation molecules. Changes in film refractive index during these various processes show that the predominantly columnar (rather than laminar) molecular arrangement established for polyelectrolyte-only films is maintained in the hybrid polymer–particle films, although the filling of the polyelectrolyte pores makes the film more isotropic.

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Optical biosensors

Ramsden¹

1997

J. Mol. Recognit.

118

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Determination of optical constants of molecular films assembled via alternate polyion adsorption

Cited by 138 publications

References 13 publications

Gold Nanoparticles on Polarizable Surfaces as Raman Scattering Antennas

Gold Nanoparticles on Polarizable Surfaces as Raman Scattering Antennas

Apparent self-accelerating alternating assembly of semiconductor nanoparticles and polymers

Optical biosensors

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