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Lee, D. H.; Condrate, R. A.

doi:10.1023/a:1004494331895

Cited by 118 publications

(76 citation statements)

References 26 publications

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“…At low surfactant concentration (Fig. 3a), the spectra indicate the presence of adsorbed carboxylate groups with a symmetric mode around 1420 cm À1 and an asymmetric mode at 1545 cm À1 [15,23]. At high surfactant concentration (Fig.…”

Section: Resultsmentioning

confidence: 89%

“…Note that the most relevant peak assignments of both in situ and ex situ spectra are presented in Table 1. The spectra of the pure surfactants are well known from literature [15,18,22]. A common feature is the olefinic CÀH stretching mode at 3006 cm À1 from the backbone of the surfactant molecules ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…2 a and b). Specific to the oleic acid spectrum is the carbonyl absorbance at 1713 cm À1 , a position that indicates that the molecules are present in dimers that are held together by hydrogen bonding [15,18]. In the oleylamine spectrum the most characteristic peak is the 787 cm À1 absorbance which can be ascribed to a NH 2 wagging vibration.…”

Section: Resultsmentioning

confidence: 99%

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Surface analysis of magnetite nanoparticles in cyclohexane solutions of oleic acid and oleylamine

Klokkenburg

Hilhorst

Erné

2007

Vibrational Spectroscopy

141

107

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The surface of magnetite (Fe 3 O 4 , d ¼ 6:3 AE 0:7 nm) nanoparticles dispersed in cyclohexane was studied in the presence of oleic acid and oleylamine using in situ FTIR spectroscopy. Equimolar mixtures of these surfactants are widely used in the chemical synthesis of nanoparticles with a low polydispersity. Here, the IR spectra indicate that oleic acid molecules adsorb to the magnetite surface as a carboxylate. Measurements as a function of surfactant concentration yield an adsorption isotherm, with about two surfactant molecules adsorbed per nm 2 of magnetite at 1 mM surfactant concentration and about 3.5 molecules per nm 2 at 310 mM, of the order expected for full monolayer coverage. No spectral indication is found of oleylamine molecules at the surface of magnetite. In solution, however, almost every oleylamine molecule combines with an oleic acid molecule to form an acid-base complex, with an association constant of 3:5 Â 10 4 dm 3 mol À1 .

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Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

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Surface analysis of magnetite nanoparticles in cyclohexane solutions of oleic acid and oleylamine

Klokkenburg

Hilhorst

Erné

2007

Vibrational Spectroscopy

141

107

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“…Starting OA-stabilizedN aYF 4 ,r espectively)o fO A. [28] After the surfacem odification with the silica shell, the characteristic vibrations of OA completely vanished from the spectra of ,which was assigned to the symmetrical stretching of Si-O-Si groups.M oreover,t wo new bands at 950 and 795 cm À1 were attributed to SiÀOH and SiO 4 vibrations, respectively.A dditional bandsa t% 3420 and 1630 cm À1 were assigned to the OÀHv ibrations of adsorbed water.A fter modification of the nanoparticles with PEI and conjugation with Al Pc-COOH, the intensiveS i-O-Si band was shifted toward lower wavenumbers.…”

Section: Resultsmentioning

confidence: 99%

Phthalocyanine‐Conjugated Upconversion NaYF₄:Yb³⁺/Er³⁺@SiO₂ Nanospheres for NIR‐Triggered Photodynamic Therapy in a Tumor Mouse Model

et al. 2017

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Photodynamic therapy (PDT) has garnered immense attention as a minimally invasive clinical treatment modality for malignant cancers. However, its low penetration depth and photodamage of living tissues by UV and visible light, which activate a photosensitizer, limit the application of PDT. In this study, monodisperse NaYF4:Yb3+/Er3+ nanospheres 20 nm in diameter, that serve as near‐infrared (NIR)‐to‐visible light converters and activators of a photosensitizer, were synthesized by high‐temperature co‐precipitation of lanthanide chlorides in a high‐boiling organic solvent (octadec‐1‐ene). The nanoparticles were coated with a thin shell (≈3 nm) of homogenous silica via the hydrolysis and condensation of tetramethyl orthosilicate. The NaYF4:Yb3+/Er3+@SiO2 particles were further functionalized by methacrylate‐terminated groups via 3‐(trimethoxysilyl)propyl methacrylate. To introduce a large number of reactive amino groups on the particle surface, methacrylate‐terminated NaYF4:Yb3+/Er3+@SiO2 nanospheres were modified with a branched polyethyleneimine (PEI) via Michael addition. Aluminum carboxyphthalocyanine (Al Pc‐COOH) was then conjugated to NaYF4:Yb3+/Er3+@SiO2‐PEI nanospheres via carbodiimide chemistry. The resulting NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc particles were finally modified with succinimidyl ester of poly(ethylene glycol) (PEG) in order to alleviate their future uptake by the reticuloendothelial system. Upon 980 nm irradiation, the intensive red emission of NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc‐PEG nanoparticles completely vanished, indicating efficient energy transfer from the nanoparticles to Al Pc‐COOH, which generates singlet oxygen (1O2). Last but not least, NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc‐PEG nanospheres were intratumorally administered into mammary carcinoma MDA‐MB‐231 growing subcutaneously in athymic nude mice. Extensive necrosis developed at the tumor site of all mice 24–48 h after irradiation by laser at 980 nm wavelength. The results demonstrate that the NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc‐PEG nanospheres have great potential as a novel NIR‐triggered PDT nanoplatform for deep‐tissue cancer therapy.

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“…One candidate would be oleic acid molecules desorbed from the surface of nanoparticles, molecules that are about 2 nm in length. However, oleic acid molecules in aprotic solvents are present as linear apolar dimers [34], which do not adsorb to the liquid-air interface; we verified that the surface tension of decalin remains unchanged (within 0:2 mN=m) after dissolution of pure oleic acid, even up to a concentration of 0:040 mol=l, twice as much as present on the particles (assuming an adsorption density of $3 nm À2 [35]) in the sample with the highest nanoparticle concentration ( ¼ 0:01). A more plausible adsorbing species is lead oleate, consisting of a Pb 2þ cation coordinated by two oleate ions and being one of the chemical precursors present during nanocrystal growth.…”

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confidence: 99%

Spatial Distribution of Nanocrystals Imaged at the Liquid-Air Interface

Rijssel¹,

Linden²,

Meeldijk

et al. 2013

Phys. Rev. Lett.

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The 3D distribution of nanocrystals at the liquid-air interface is imaged for the first time on a singleparticle level by cryogenic electron tomography, revealing the equilibrium concentration profile from the interface to the bulk of the liquid. When the surface tension of the liquid is decreased, the interaction of the nanocrystals with the liquid-air interface shifts from adsorption to desorption. Macroscopic surface tension measurements do not detect this transition, due to the presence of surface-active molecular species.

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Cited by 118 publications

References 26 publications

Surface analysis of magnetite nanoparticles in cyclohexane solutions of oleic acid and oleylamine

Surface analysis of magnetite nanoparticles in cyclohexane solutions of oleic acid and oleylamine

Phthalocyanine‐Conjugated Upconversion NaYF₄:Yb³⁺/Er³⁺@SiO₂ Nanospheres for NIR‐Triggered Photodynamic Therapy in a Tumor Mouse Model

Spatial Distribution of Nanocrystals Imaged at the Liquid-Air Interface

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Untitled

Cited by 118 publications

References 26 publications

Surface analysis of magnetite nanoparticles in cyclohexane solutions of oleic acid and oleylamine

Surface analysis of magnetite nanoparticles in cyclohexane solutions of oleic acid and oleylamine

Phthalocyanine‐Conjugated Upconversion NaYF4:Yb3+/Er3+@SiO2 Nanospheres for NIR‐Triggered Photodynamic Therapy in a Tumor Mouse Model

Spatial Distribution of Nanocrystals Imaged at the Liquid-Air Interface

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Phthalocyanine‐Conjugated Upconversion NaYF₄:Yb³⁺/Er³⁺@SiO₂ Nanospheres for NIR‐Triggered Photodynamic Therapy in a Tumor Mouse Model