Tetradecylphosphonic Acid Research Articles

(Na,K)NbO3 nanoparticle-embedded piezoelectric nanofiber composites for flexible nanogenerators

Abstract Piezoelectric composite nanofibers based on (Na 0.5 ,K 0.5 )NbO 3 (NKN) nanoparticles embedded in poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] polymer are investigated in terms of their performance as nanogenerators. Perovskite NKN nanoparticles with ∼30–105 nm were separately prepared by combustion synthesis using polyacrylic acid (PAA) as a fuel. Surface modification of nanoparticles by tetradecylphosphonic acid (TDPA) was essential to secure proper adhesion with the polymer in the nanofibers prepared by electrospinning. Location-dependent piezoelectricity measurements confirmed that the region of embedded NKN filler particles exhibited better piezoelectricity than the P(VDF–TrFE) matrix region. Energy harvesting performance of the flexible composite nanogenerator demonstrated ∼0.98 V output voltage and ∼78 nA output current, which were enhanced depending on the volume fraction of the NKN nanoparticles dispersed in the polymer.

Self-organization of nanorods into ultra-long range two-dimensional monolayer end-to-end network.

Highly uniform large-scale assembly of nanoscale building blocks can enable unique collective properties for practical electronic and photonic devices. We present a two-dimensional (2-D), millimeter-scale network of colloidal CdSe nanorods (NRs) in monolayer thickness through end-to-end linking. The colloidal CdSe NRs are sterically stabilized with tetradecylphosphonic acid (TDPA), and their tips are partially etched in the presence of gold chloride (AuCl3) and didecyldimethylammonium bromide (DDAB), which make them unwetted in toluene. This change in surface wetting property leads to spontaneous adsorption at the 2-D air/toluene interface. Anisotropy in both the geometry and the surface property of the CdSe NRs causes deformation of the NR/toluene/air interface, which derives capillary attraction between tips of neighboring NRs inward. As a result, the NRs confined at the interface spontaneously form a 2-D network composed of end-to-end linkages. We employ a vertical-deposition approach to maintain a consistent rate of NR supply to the interface during the assembly. The rate control turns out to be pivotal in the preparation of a highly uniform large scale 2-D network without aggregation. In addition, unprecedented control of the NR density in the network was possible by adjusting either the lift-up speed of the immersed substrate or the relative concentration of AuCl3 to DDAB. Our findings provide important design criteria for 2-D assembly of anisotropic nanobuilding blocks.

Deciphering ligands' interaction with Cu and Cu2O nanocrystal surfaces by NMR solution tools.

The hydrogenolysis of [Cu2{(iPrN)2(CCH3)}2] in the presence of hexadecylamine (HDA) or tetradecylphosphonic acid (TDPA) in toluene leads to 6-9 nm copper nanocrystals. Solution NMR spectroscopy has been used to describe the nanoparticle surface chemistry during the dynamic phenomenon of air oxidation. The ligands are organized as multilayered shells around the nanoparticles. The shell of ligands is controlled by both their intermolecular interactions and their bonding strength on the nanocrystals. Under ambient atmosphere, the oxidation rate of colloidal copper nanocrystals closely relies on the chemical nature of the employed ligands (base or acid). Primary amine molecules behave as soft ligands for Cu atoms, but are even more strongly coordinated on surface Cu(I) sites, thus allowing a very efficient corrosion protection of the copper core. On the contrary, the TDPA ligands lead to a rapid oxidation rate of Cu nanoparticles and eventually to the re-dissolution of Cu(II) species at the expense of the nanocrystals.

Shell deposition of CdSe nano dots and rods

To investigate the shell deposited kinetics, CdSe quantum dots (QDs) and nanorods (NRs) with a maximum length of 17 nm were fabricated via organic synthesis routes. CdSe with a hexagonal crystal structure (wurtzite) favors epitaxial growth on the {002} surfaces when well-controlled conditions were used. The morphologies and sizes of CdSe samples depended strongly on chemicals and temperature. In the case of 320 °C, CdSe NRs with adjusted length of 7–17 nm were obtained from trioctylphosphine oxide (TOPO) and tetradecylphosphonic acid (TDPA). In contrast, short CdSe NRs (less than 10 nm) were created from octadecylphosphonic acid (ODPA) and trioctylamine (TOA). Spherical CdSe QDs were further fabricated using stearic acid (SA) and TOPO at 300 °C. CdSe cores were coated with Cd0.5Zn0.5S and CdTe shells. Anisotropic growth occurred during shell deposition because CdS shells grown preferentially on the {001} facet of the CdSe core. In the case of CdSe core prepared from TOPO and TDPA, CdSe/Cd0.5Zn0.5S core/shell samples prepared from long CdSe NRs (more than 10 nm) revealed a peanut morphology while the core/shell samples created from short ones (less than 10 nm) exhibited a spherical morphology. All of the CdSe/Cd0.5Zn0.5S core/shell samples revealed a similar length to that of the CdSe cores. This phenomenon was also observed for the core/shell samples fabricated using CdSe NRs prepared by ODPA and TOA. This is ascribed to the well-developed crystal structure of CdSe NRs fabricated using an organic synthesis at high temperature. In contrast, this anisotropic growth did not occur when spherical CdSe QDs prepared from SA and TOPO and the shell (Cd0.5Zn0.5S) coating carried out using SA and TOA. To indicate the shell depositing process, CdSe NRs fabricated using TDPA and TOPO were coated with a CdTe shell. CdTe monomers were deposited on the middle and tip parts of the CdSe NRs to form a tetrapod-like morphology at 220 °C. This is ascribed to the large difference of structure of CdSe (hexagonal) and CdTe (zinc blende).

Characterization of Self-Assembled Monolayer on Anodized Aluminum by XPS, AFM and Low-Voltage SEM

Organic layers of tetradecylphosphonic acid (TDP) and octadecyltrietoxysilane (OES) are formed on flat anodized aluminum surfaces by a simple immersion process. The organic layers are characterized by dynamic contact angle measurements for water, AFM, low-voltage SEM and angle-resolved XPS. The results indicate that a self-assembled monolayer is formed using TDP, but not for OES. Plasma surface treatment prior to the coating was found to significantly influence the formation of organic layers.

Surface Chemistry of CdTe Quantum Dots Synthesized in Mixtures of Phosphonic Acids and Amines: Formation of a Mixed Ligand Shell

Solution nuclear magnetic resonance (NMR) spectroscopy is used to analyze the surface chemistry of CdTe quantum dots (QDs) synthesized in the presence of tetradecylphosphonic acid and oleylamine. The resulting CdTe QDs have a mixed capping, composed of tightly bound phosphonate anhydride and amine ligands. The overall ligand density is relatively low, which concurs with a low Cd excess in the QDs. We find that upon addition of oleic acid, neither amine or phosphonate anhydride ligands are released from the QDs. On the other hand, the addition of phosphonic acids to CdTe QDs partially capped by oleic acid moieties through a high temperature ligand exchange process leads to the ready, one-to-one release of oleic acid. A full thermodynamic analysis of the phosphonate/carboxylate exchange is however not possible since the exchange appears to be modified by the forced ligand exchange used to replace phosphonate by carboxylate ligands.

Exceptional Thermal Stability of Pd@CeO2 Core–Shell Catalyst Nanostructures Grafted onto an Oxide Surface

Monolayer films of highly catalytically active Pd@CeO2 core-shell nanocomposites were grafted onto a planar YSZ(100) (yttria-stabilized zirconia, YSZ) single crystal support that was functionalized with a CVD-deposited layer of triethoxy(octyl)silane (TEOOS). The resulting monolayer films were found to exhibit exceptionally high thermal stability compared to bare Pd nanoparticles with the Pd@CeO2 nanostructures remaining intact and highly dispersed upon calcining in air at temperatures in excess of 1000 K. The CeO2 shells were also shown to be more easily reduced than bulk CeO2, which may partially explain their unique activity as oxidation catalysts. The use of both TEOOS and tetradecylphosphonic acid (TDPA) as coupling agents for dispersing Pd@CeO2 core-shell nanocomposites onto a high surface area γ-Al2O3 support is also demonstrated.

Photochemical properties and shape evolution of CdSe QDs in a non-injection reaction

Highly monodispersed CdSe quantum dots (QDs) were prepared without an injection procedure. A series of Cd salts of long chain fatty acids, including Cd-myristate (C14), Cd-palmitate (C16) and Cd-stearate (C18) was prepared, and all metallic precursors and surfactants were mixed together followed by increasing the temperature in a controlled manner. The reaction resulted in highly monodisperse and bright zinc blende QDs. In addition, the effects of specific ligands which have been known to lead anisotropic growth of the nanocrystals in the injection method were investigated. The use of alkyl phosphonic acid and alkyl amine was found to produce extremely monodisperse CdSe QDs with a high quantum yield. This procedure was proven to be able to yield a large quantity of zinc blende CdSe QDs (2 g) in a one-pot reaction. The use of a controlled amount of tetradecylphosphonic acid and octadecylamine resulted in tetrapod- and match-shaped QDs, the first reported by a non-injection method. These results clearly demonstrate that appropriate combination of precursors can provide high quality of CdSe nanocrystals in terms of quantum yield, monodispersity and shape control by a non-injection method.

Tetradecylphosphonic acid modified BaTiO3 nanoparticles and its nanocomposite

Surface-functionalization of BaTiO3 nanoparticles and subsequent utilization of simple solution casting to yield the good compatible PVDF nanocomposites were investigated. 1-Tetradecylphosphonic acid (TDPA) was synthesized and then used to functionalize the surface of BaTiO3 nanoparticles. The prepared TDPA–BaTiO3 nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). These results indicated that the surface of nanoparticles was grafted successfully with such phosphonic acid. Also, the existing ligands of surface were examined, and the coverage onto surface of BaTiO3 nanoparticles evaluated by thermogravimetric analysis (TGA) was 25.1%. The dispersion of modified nanoparticles in ethanol and dichloromethane was significantly improved. Besides of good flexibility, PVDF nanocomposite film with volume fraction of 40vol.% modified nanofillers exhibited high dielectric constant and low dielectric loss.

Crystallization kinetics and phase transformation of poly(vinylidene fluoride) films incorporated with functionalized baTiO3 nanoparticles

AbstractThe transformation of α to β‐phase in poly(vinylidene fluoride) (PVDF) induced by the addition of tetradecylphosphonic acid (TDPA)‐BaTiO3 nanoparticles and subsequently the isothermal crystallization kinetics of pristine PVDF and its nanocomposites have been investigated. The result of infrared spectra showed that the relative crystalline fraction of β‐phase was enhanced greatly after the introduction of TDPA–BaTiO3 nanoparticles, and reached the peak of 93% when the concentration of nanofillers was 20%. The interaction between TDPA–BaTiO3 nanoparticles and PVDF macromolecular chains induced the change of conformation from trans‐gauche to all‐trans crystal structure in PVDF segment. The isothermal crystallization of TDPA–BaTiO3/PVDF nanocomposites was carried out by the differential scanning calorimetry (DSC). The influence of TDPA–BaTiO3 nanoparticles concentration on crystallization rate, activate energy, melting enthalpy, and peak temperature were studied. The nanocomposite film loaded 20% TDPA–BaTiO3 nanoparticles exhibited the highest crystallization rate and activate energy, which decreased after loading more nanofillers in the host because of high volume fraction of nanoparticles leading to steric hindrance and further weakening the mobility of PVDF chains during the crystallization. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Observation of self‐assembled layers of alkyl phosphonic acid on aluminum using low‐voltage scanning electron microscopy and AFM

Self‐assembled alkyl phosphate layers have been formed on a flat, anodized aluminum substrate in dilute ethanol solution containing 2 wt% n‐tetradecylphosphonic acid (TDP) and examined by low‐voltage scanning electron microscopy as well as atomic force microscopy and X‐ray photoelectron spectroscopy. Locally, multi‐layered alkyl phosphate films have been formed on aluminum, being clearly observed by a low‐voltage scanning electron microscope operated at less than 1 kV. Atomic force microscopy observations disclosed that bilayers of tetradecylphosphonic acid are stacked on the substrate to form multilayers. The present study revealed that the uniform self‐organized monolayer is not always formed readily on an oxidized aluminum surface. Copyright © 2013 John Wiley & Sons, Ltd.

Self-assembling behavior and corrosion inhibition properties of TDPA films on differently structured surfaces of 2024 and 1060 aluminum alloys

AbstractThe adsorption and corrosion inhibition behavior of 1–tetradecylphosphonic acid self-assembled monolayers on the differently structured surfaces of 2024 and 1060 aluminum alloys were investigated by contact-angle measurement, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy coupled with energy-dispersive spectroscopy. The electrochemical experiments showed that a 4 h modification of 2024 and 1060 alloys resulted in a maximal inhibition efficiency. Independent of assembly time, the desorption of the tetradecylphosphonic acid molecules provoked by anodic polarization to a certain degree resulted in the acceleration of the anodic dissolution reaction. The inhibition of the self-assembled monolayers for the 1060 alloy was more prominent than for the 2024 alloy. This is consistent with the contact-angle values, supporting the conclusion that TDPA formed a more closely packed SAM on the surface of the 1060 alloy than of the 2024 alloy. Scanning electron microscopy/energy dispersive X-ray spectroscopy results directly revealed the inhibition effect of the monolayers on the primary corrosion stage of these two alloys.

Dark-red-emitting CdTe/Cd1-xZnxS core/shell quantum dots: preparation and properties

CdTe nanocrystals (NCs) were fabricated through an organic synthesis. The growth and properties of CdTe NCs depended strongly on the preparation conditions. In a reaction system of octadecene and tetradecylphosphonic acid (TDPA), the growth was slow. CdTe NCs with cubic-like morphology were created in trioctylamine (TOA) using octadecylphosphonic acid (ODPA)-CdO or TDPA-CdO as precursors. The TOA and ODPA system gives rise to NCs with high photoluminescence (PL) efficiencies (12%). A Cdx Zn1-x S shell coating on the CdTe core, gave rise to tunable dark red PL (630-670 nm). The morphology and PL properties of the CdTe cores were drastically affected by shell coating and this determined the properties of CdTe/Cdx Zn1-x S NCs. Small CdTe NCs were easily coated with Cdx Zn1-x S shells. The resulting core/shell NCs revealed a spherical morphology. However, shell growth became slow when large CdTe cores were used. This is ascribed to the cores with a cubic-like morphology. CdS interlayer plays an important role for the formation of the CdTe/Cdx Zn1-x S NCs because the experimental result indicated it is difficult to coat CdTe NCs with a ZnS shell. The core/shell NCs benefited from a Cdx Zn1-x S composite shell because CdTe/CdS NCs created via a similar procedure revealed a low PL efficiency.

Ligand Exchange on Colloidal CdSe Nanocrystals Using Thermally Labile tert-Butylthiol for Improved Photocurrent in Nanocrystal Films

As-prepared CdSe nanocrystals were ligand exchanged using tert-butylthiol, which yielded stable CdSe nanocrystal inks in the strong donor solvent tetramethylurea. The efficacy of ligand exchange was probed by thermogravimetric analysis (TGA) and FT-IR spectroscopy. By studying sequential exchanges of tetradecylphosphonic acid and then tert-butylthiol, TGA and energy dispersive X-ray spectroscopic evidence clearly demonstrated that the ligand exchange is essentially quantitative. The resulting tert-butylthiol-exchanged CdSe nanocrystals undergo facile thermal ligand expulsion (≤200 °C), which was studied by TGA-mass spectrometry. Mild thermal treatment of tert-butylthiol-exchanged CdSe nanocrystal films was found to induce loss of quantum confinement (as evidenced by UV-vis spectroscopy) and provided for increased electrochemical photocurrent, electron mobility, and film stability. Pyridine-exchanged CdSe nanocrystals were employed as a control system throughout to demonstrate the beneficial attributes of tert-butylthiol exchange; namely, lower organic content, better colloidal stability, improved interparticle coupling, and vastly increased electrochemical photocurrent response upon illumination.

Spatial control of the threshold voltage of low-voltage organic transistors by microcontact printing of alkyl- and f luoroalkyl-phosphonic acids

Abstract

Synthesis of calcium–silica composites: A route toward an in vitro model system for calcific band keratopathy precipitates

Calcific band keratopathy (CBK) is a degenerative condition resulting in the deposition of calcium salts in the superficial layers of the cornea and causing significant visual disturbance and pain of the affected eye. Unfortunately, the amount of CBK precipitates recovered from the affected eye is very small therefore; it would be beneficial to prepare a synthetic material mimicking CBK material to further the development of therapeutics. Analyses of biological samples recovered from patients show the presence of silicon in addition to calcium, as well as a distinctive fused spherical morphology. This prompted us to study the reaction of various sources of silicon (fumed silica, silicic acid, and silicone oil) with CaCO(3) under a range of reaction conditions to gain an understanding of the formation of CBK. A silicon source alone was not found to be responsible for the fused spherical morphology, and a third component, a polar surfactant-like molecule such as sodium dodecyl sulfate or tetradecylphosphonic acid, was also required. The effects of silicon:calcium ratio and reaction time have been studied. The reaction of fumed silica with CaCO(3) in presence of sodium dodecyl sulfate results in the formation of spherical shapes resembling the structures and chemical composition observed in the eye samples, while no such structures were observed in the absence of silicon. Samples closely resembling human samples were also formed from the reaction of silicone oil with CaCO(3) in the presence of tetradecylphosphonic acid. Samples were characterized by SEM, XRD, and XPS and Raman spectroscopy.

Synthesis of PbSe nanowires: the impact of alkylphosphonic acid addition

Reaction of Pb oleate with trioctylphosphine (TOP)/Se in 1-octadecene under appropriate conditions yields PbSe nanowires. The parameters found to be critical for the isolation of exclusively one-dimensional material are the Pb : Se ratio and the temperature profile used during synthesis. Addition of strongly coordinating tetradecylphosphonic acid (TDPA) to the system has a profound impact on the surface morphology, with increasing TDPA concentration producing narrower, smoother nanowires when all other parameters are held constant. The wire morphology and structural data are consistent with a combination of oriented attachment on 〈111〉 surfaces, yielding wires with a [100] axial orientation, and a ligand-mediated competition between growth on 〈111〉, 〈110〉 and 〈100〉 planes. The products possess 10–20 nm diameters, with lengths generally over one micron, and have been characterized through SEM, TEM, EDS, electron diffraction, and optical spectroscopy.

Room‐Temperature Formation of Hollow Cu2O Nanoparticles

Monodisperse Cu and Cu2O nanoparticles (NPs) are synthesized using tetradecylphosphonic acid as a capping agent. Dispersing the NPs in chloroform and hexane at room temperature results in the formation of hollow Cu2O NPs and Cu@Cu2O core/shell NPs, respectively. The monodisperse Cu2O NPs are used to fabricate hybrid solar cells with efficiency of 0.14percent under AM 1.5 and 1 Sun illumination.

Partitioning of hydrophobic CdSe quantum dots into aqueous dispersions of humic substances: Influence of capping-group functionality on the phase-transfer mechanism

Studies of the fate and transport of engineered nanomaterials are invaluable in predicting environmental impact, bioavailability, and toxicity. We report on the influence of humic and fulvic acids (models of natural organic matter) on the phase transfer of organic-capped CdSe quantum dots (QDs) from hexane to water. QDs capped with tri- n-octylphosphine oxide, tetradecylphosphonic acid, and oleic acid, which were otherwise insoluble in water, were transferred into aqueous solutions of humic substances (HS) (Suwannee River humic acid and fulvic acid standards) within 1–10 days after mixing. Phase transfer was characterized by infrared and UV/Vis absorption spectroscopy, emission spectroscopy, dynamic light scattering, electron microscopy, and inductively coupled plasma mass spectrometry. Phase-transferred QDs were intact and temporarily stabilized by HS. On longer timescales, Cd 2+ leached into aqueous solution. Our data suggest that two mechanisms promote the phase transfer of QD–HS agglomerates: (1) an overcoating mechanism involving dispersion interactions between non-polar moieties of HS and hydrocarbon chains of organic capping groups and (2) a coordinative mechanism involving displacement of capping groups by Lewis basic functionalities of HS. The structure of the capping group of QDs influenced the relative contributions of the two mechanisms and the extent to which Cd 2+ leached into water.

CdSe Quantum Rod Formation Aided By In Situ TOPO Oxidation.

In-situ TOPO decomposition was accomplished by applying a vacuum at elevated temperatures to a precursor solution in the presence of oxygen, leading TOPO to oxidize to di-n-octylphosphinic acid (DOPA) and octylphosphonic acid (OPA). The mixed ligand system of tetradecylphosphonic acid (TDPA), DOPA and OPA produced CdSe QRs on the order of 4 nm in diameter and 20 nm in length. Solvent and ligand identification was performed by mass spectrometry and (31)P nuclear magnetic resonance spectroscopy. Transmission electron microscopy (TEM) was utilized to determine the morphology, size and crystal growth of the CdSe QRs. This method of CdSe QR synthesis is unique in that the phosphonic acids responsible for anisotropic growth are formed in situ, prior to the nucleation and growth of the nanorods. Without the oxidation of TOPO, CdSe quantum dots (QDs) were synthesized instead, as reported previously. This discovery reinforces the efficacy of DOPA and OPA molecules as critical ligands in the formation of 1-dimensional (1D) nanostructures.