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This is the first report on the critical nature of nanolattice formability of different particle sizes (∼4–10 nm) of monodispersed nickel nanoparticles. They exhibit strikingly hexagonal close-packed (hcp) nanolattices without extra forces whenever trioctylphosphine (TOP) is one of the surfactant(s). This clearly establishes the unique role of nanolattice formability of TOP. The c/a ratios are interestingly identical to those of atomic lattices. An attempt has also been made to explain them based on the balanced attractive and repulsive forces of the surfactant-generated cation–anion pairs on the surface of the nanoparticles. The present findings therefore will provide a far-reaching vista for the fabrication of varieties of natural nanolattices and their understanding on applications in a new paradigm.

We present an effective way to boost the as-synthesized CdSe quantum dot-sensitized solar cells (QDSSCs) performance by introducing an inorganic ligand exchange strategy into this traditional system. Inorganic ligand exchange, to the best of our knowledge, is designed for the first time for CdSe-based QDSSCs, and it features low-cost, easy operation, and repeatable process. The route involves the direct deposition of the CdSe quantum dots (QDs), which were initially capped with trioctylphosphine (TOP) ligands onto mesoporous TiO2 nanocrystalline electrodes and followed by a post-treatment of the sensitized photoanode films with sulfur ions (S2–) solution. Here, changes in surface chemical status of CdSe QDs during the inorganic ligand exchange process and the influence of ligand exchange on the electron’s ultralfast transfer between nanoparticles were investigated through XPS and femtosecond transient grating techniques, respectively. With the inorganic ligand passivated CdSe QDs, the QDSSCs exhibited a p...

We report the development of Co9S8 nanocrystals as a cost-effective cathode material that can be readily combined with spraying techniques to fabricate large-area dye-sensitized solar cell (DSSC) devices and can be further connected with series or parallel cell architectures to obtain a relatively high output voltage or current. A gram-scale synthesis of Co9S8 nanocrystal is carried out via a noninjection reaction by mixing anhydrous CoCl2 with trioctylphosphine (TOP), dodecanethiol and oleylamine (OLA) at 250 °C. The Co9S8 nanocrystals possess excellent catalytic ability with respect to I(-)/I3(-) redox reactions. The Co9S8 nanocrystals are prepared as nanoinks to fabricate uniform, crack-free Co9S8 thin films on different substrates by using a spray deposition technique. These Co9S8 films are used as counter electrodes assembled with dye-adsorbed TiO2 photoanodes to fabricate DSSC devices having a working area of 2 cm(2) and an average power conversion efficiency (PCE) of 7.02 ± 0.18% under AM 1.5 solar illumination, which is comparable with the PCE of 7.2 ± 0.12% obtained using a Pt cathode. Furthermore, six 2 cm(2)-sized DSSC devices connected in series output an open-circuit voltage of 4.2 V that can power a wide range of electronic devices such as LED arrays and can charge commercial lithium ion batteries.

The effect of trioctylphosphine (TOP) concentration on the growth of nickel nanoparticles is studied using in situ synchrotron small-angle X-ray scattering. The growth kinetics are fitted using a two-step nucleation and autocatalytic growth model. TOP acts as a nucleating agent and then acts as an inhibitor against rapid particle growth. Increasing the TOP concentration results in smaller nanoparticles. Once there is a critical concentration of nickel particles above a certain size, they start to aggregate. This results in a broadening of the particle size distribution at later times due to particles on the outside of the aggregates continuing to grow, while those on the inside cease to grow as the nickel precursor is locally depleted.

This paper reports the preparation of Cu2 ZnSnSe4 (CZTSe) nanocrystals from elemental sources through the application of various coordinating solvents. The CZTSe nanocrystals were synthesized by mixing metals in oleylamine (OLA) and isophorondiamine (IPDA) at a ratio of 1:3 as well as a Se solution in trioctylphosphine (TOP) under N2 flow at atmospheric pressure at a reaction temperature of 235 °C. X-ray diffraction and Raman spectroscopy were used to track the reaction mechanisms associated with various solvents. A growth mechanism, distinct from that associated with TOP/OLA, promoted the formation of nanoparticles and improved the reactivity provided by the addition of IPDA solvent through double N-chelation. The reaction mechanism involved in stannite Cu2 ZnSnSe4 phase crystallization from Cu2 SnSe3 and ZnSe is supported by theoretical analysis. The monodispersed CZTSe nanocrystals are polycrystalline and 20-30 nm in size. Optical measurements revealed a direct band gap of 1.42 eV. This study presents a relatively simple, low cost coordinating solvent route for the synthesis of CZTSe nanoparticles, applicable to the fabrication of low-cost thin-film solar cells.

The synthesis of monodisperse 5-10 nm Pd5P2 catalytic particles by encapsulation in a mesoporous silica network, along with preliminary data on hydrodesulfurization (HDS) activity, is reported. Precursor Pd-P amorphous nanoparticles are prepared by solution-phase reaction of palladium(II) acetylacetonate with trioctylphosphine at temperatures up to 300 °C. Direct crystallization of Pd5P2 in solution by increasing the temperature to 360 °C leads to sintering, but particle size can be maintained during the transformation by encapsulation of the amorphous Pd-P particles in a mesoporous silica shell, followed by treatment of the solid at 500 °C under a reducing atmosphere, yielding Pd5P2@mSiO2. The resultant materials exhibit high BET surface areas (1000 m(2)/g) and an average pore size of 3.7 nm. Access to the catalyst surface is demonstrated by dibenzodithiophene (DBT) HDS testing. Pd5P2@mSiO2 shows a consistent increase in HDS activity as a function of temperature, with DBT conversion approaching 60% at 402 °C. The ability to control particle size, phase, and sintering is expected to enable the fundamental catalytic attributes that underscore activity in Pd5P2 to be assessed.

We report a procedure to prepare highly monodisperse copper telluride nanocubes, nanoplates, and nanorods. The procedure is based on the reaction of a copper salt with trioctylphosphine telluride in the presence of lithium bis(trimethylsilyl)amide and oleylamine. CuTe nanocrystals display a strong near-infrared optical absorption associated with localized surface plasmon resonances. We exploit this plasmon resonance for the design of surface-enhanced Raman scattering sensors for unconventional optical probes. Furthermore, we also report here our preliminary analysis of the use of CuTe nanocrystals as cytotoxic and photothermal agents.

Tin sulfide (SnS), having a direct band gap of 1.3 eV, is a promising absorber material for solar energy conversion. We synthesized colloidal SnS nanocrystals with a size tuneable from 5 to 20 nm and low size dispersion. These nanocrystals can be processed as thin films using low-cost solution phase methods. They also offer the possibility of controlling the crystalline phase before deposition. With the goal to obtain dense and crack-free films of high conductivity, we used a layer-by-layer deposition technique. In the first step, the substrate was dipped in the nanocrystal colloidal solution (“ink”). Next, exchange of the nanocrystal surface ligands (oleylamine, trioctylphosphine, oleic acid) was carried out by dipping the substrate into a solution of small cross-linking molecules (1,4-benzenedithiol). This exchange enhances the electronic coupling and charge carrier mobilities by reducing the interparticle distance. At the same time it assures the immobilization of the nanocrystals to avoid their removal during subsequent depositions. The thickness of the nanocrystal thin films was controlled in a range of 100–250 nm by varying the number of the alternating nanocrystal deposition and ligand exchange steps. Scanning electron microscopy and atomic force microscopy investigations show that the obtained films are dense and homogeneous with a surface roughness as low as 3 to 4 nm root mean square. Using an inverted structure, the heterojunction of a SnS nanocrystals film with n-type ZnO nanocrystals shows a strongly increased current density under white light irradiation with respect to the dark.

The electronic properties of metal surfaces can be modulated to weaken the binding energy of adsorbed H-intermediates on the catalyst surface, thus enhancing catalytic activity for the hydrogen evolution reaction (HER). Here we first prepare PdCu alloy nanocubes (NCs) by coreduction of Cu(acac)2 (acac = acetylacetonate) and Na2PdCl4 in the presence of oleylamine (OAm) and trioctylphosphine (TOP). The PdCu NC coated glassy carbon electrode is then anodized at a constant potential of 0.51 V vs Ag/AgCl at room temperature in 0.5 M H2SO4 solution for 10 s, which converts PdCu NCs into core@shell PdCu@Pd NCs that show much enhanced Pt-like activity for the HER and much more robust durability. The improvements in surface property and HER activity are rationalized based on strain and ligand effects that enhance the activity of the edge-exposed Pd atoms on core@shell PdCu@Pd structure. This work opens up a new perspective for simultaneously reducing metal Pd cost and achieving excellent performance toward the HER.

Appropriate surface ligands are required for tuning the physicochemical and photophysical properties of nanoclusters (NCs). These surface ligands are especially critical for passivating the small (CdSe)33,34 NCs where the majority of atoms are at the NC surface. In this study, triphenylphosphine (TPP), trioctylphosphine (TOP) and tris(pentafluorophenyl)phosphine (TPFP) have been tested as capping agents for alkylamine-coated CdSe NCs. TPP and TOP compounds are found to increase the quantum yield of photoluminescence (PL) from 0.15% to 0.6% and 0.53%, respectively, and to preserve this increased PL with time, probably by preventing charge leakage as a result of their binding to Se atoms. Since no dramatic change in the shape of NCs' PL spectrum occurs after surface treatment, both the exciton band and the low-energy broad band in magic NCs are thought to describe the intrinsic luminescence properties of the NCs. As a result, the PL increase due to Se passivation is thought to be mainly caused by a decrease in the efficiency of the NC nonradiative pathways.

Separation of magic size clusters (MSCs) from monodisperse quantum dots (QDs) has generally been a difficult task while employing the commonly used synthesis procedure, where for preparation of PbSe QDs, Se-TOP (TOP = trioctylphosphine) is injected into Pb-oleate in 1-octadecene medium. In this study, we report for the first time a simple method to prepare MSCs, QDs and particles close to the bulk of PbSe using oleylamine (OAM) as the reducing agent, where the individual entities are efficiently separated. The chemical yield is found to be 95%. Studies on optical properties revealed the absorption and emission peaks of MSCs at fixed positions of 600 and 780 nm, respectively, while QDs exhibit significant shift to longer wavelengths for both the cases, depending on the particle size. Shift of the emission peak position for QDs is observed to be larger for initial stages of the waiting time as compared to those for longer waiting times. This can be attributed to two factors: faster growth in particle size is favoured kinetically in the initial stages, while thermodynamic stability occurs in the later stages, and reduction in surface to core contribution with increase of waiting time. QDs were found to emit at only one particular wavelength while they absorbed at two or more wavelengths. The quantum yields (QYs) of particles of sizes 4.1 and 5.1 nm are found to be 80 and 30%, respectively. The lifetime values are found to be 1.0-1.3 μs for QDs having an emission peak in the range of 1300-1500 nm. The hybrid device of PbSe (5 nm size) and MEHPPV (2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) shows increased conductivity both in the dark and in light, due to absorption in the region of NIR photons in the former and additionally in the visible region in the latter.

Nickel nanoparticles (NPs) were prepared by thermal decomposition method using Oleylamine (OLY) as a solvent and Trioctylphosphine (TOP) as a surfactant. We have investigated the effect of pH and addition of Ethylenediamine tetraacetic acid (EDTA) on the stability and particle size of Ni NPs using zeta potential and particle size analyser. Coating of the surfactants on the surface of Ni NPs was confirmed by Fourier transform infrared (FTIR) spectroscopy. Autotitration study of zeta potential of these NPs in ethanol by dynamic light scattering (DLS) at different pH values confirmed an isoelectric point (IEP) at pH = 3.64 in ethanol and pH = 3.04 after addition of EDTA in ethanol. It was observed that addition of EDTA in nanosuspension enhances stability of Ni-NPs significantly.

CdTe nanocrystals were synthesized by the hot-injection method with a mixture of oleylamine and octadecene as a solvent. The influence of the composition of the solvent and of the injection solution on the shape of CdTe nanoparticles was investigated. Various shapes of CdTe nanocrystals, such as nanodots, nanorods, multipods, and nanowires, could be obtained by changing the reaction conditions. Tuning the reactivity of both the cadmium and the tellurium precursors at the same time was found to be the main reason for the shape control of CdTe nanocrystals in this reaction system. The reactivity of the Cd precursor was controlled by the composition of the solvent, while the activity of the Te precursor could be influenced by using trioctylphosphine and tributylphosphine in the injection solution.

We propose the synthesis and characterization of colloidal aluminium selenide nanocrystals using trioctylphosphine as a solvent. The nanoparticles have several absorption bands in the spectral region 330–410 nm and are bright UV-blue luminescent, which is well demanded in light collecting and emitting devices, e.g. for tuning their spectral characteristics to higher energy solar photons.

Hydrophobic CdSe/Cd0.5Zn0.5S core-shell quantum dots (QDs) with high photoluminescence (PL) efficiency and tunable PL have been fabricated through a controlled two-step synthesis. The size of CdSe cores depended strongly on the injection speed of trioctylphosphine selenium and reaction temperature and time. With increasing size, the morphology of the cores varied from spherical to rod. A Cd05Zn0.5S shell coating resulted in a high PL efficiency up to 80% and tunable PL spectra from green to red. Because resulting core/shell QDs exhibited narrow PL spectra (full-width at half-maximum of less than 30 nm) and high PL efficiencies, they were surface-modified by a SiO2 layer with functional groups for biological applications through a controlled reverse micelle route. Partially hydrolyzed tetraethyl orthosilicate (TEOS) play an important role for the QDs transferred into water phase from oil phase. The thickness of SiO2 layer was adjusted less than 5 nm through controlling the amount of TEOS and reaction time. Aminopropyltrimethoxysilane were added to attach functional groups on the SiO2 layer of the QDs. The functional SiO2-coated QDs were conjugated with immunoglobin G (IgG) antibody by using small molecules as cross linkers. Because the QDs revealed a high PL efficiency up to 30% after conjugation with IgG, they will have important applications in biological and medical research fields.

In this study, benzenethiol ligands were applied to the surface of CdSe@ZnS core@shell quantum dots (QDs) and their effect on the performance of quantum dot light-emitting diodes (QD-LEDs) was investigated. Conventional long-chained oleic acid (OA) and trioctylphosphine (TOP) capping ligands were partially replaced by short-chained benzenethiol ligands in order to increase the stability of QDs during purification and also improve the electroluminescence performance of QD-LEDs. The quantum yield of the QD solution was increased from 41% to 84% by the benzenethiol ligand exchange. The mobility of the QD films with benzenethiol ligands approximately doubled to 2.42 × 10−5 cm2 V−1 s−1 from 1.19 × 10−5 cm2 V−1 s−1 compared to the device consisting of OA/TOP-capped QDs, and an approximately 1.8-fold improvement was achieved over QD-LEDs fabricated with bezenethiol ligand-exchanged QDs with respect to the maximum luminance and current efficiency. The turn-on voltage decreased by about −0.6 V through shifting the energy level of the QDs with benzenethiol ligands compared to conventional OA and TOP ligands.

Monodisperse Ni/Pd core/shell nanoparticles (NPs) have been synthesized by sequential reduction of nickel(II) acetate and palladium(II) bromide in oleylamine (OAm) and trioctylphosphine (TOP). The Ni/Pd NPs have a narrow size distribution with a mean particle size of 10 nm and a standard deviation of 5% with respect to the particle diameter. Mechanistic studies showed that the presence of TOP was essential to control the reductive decomposition of Ni-TOP and Pd-TOP, and the formation of Ni/Pd core/shell NPs. Using the current synthetic protocol, the composition of the Ni/Pd within the core/shell structure can be readily tuned by simply controlling the initial molar ratio of the Ni and Pd salts. The as-synthesized Ni/Pd core/shell NPs were supported on graphene (G) and used as catalyst in Suzuki-Miyaura cross-coupling reactions. Among three different kinds of Ni/Pd NPs tested, the Ni/Pd (Ni/Pd = 3/2) NPs were found to be the most active catalyst for the Suzuki-Miyaura cross-coupling of arylboronic acids with aryl iodides, bromides and even chlorides in a dimethylformamide/water mixture by using K2CO3 as a base at 110 °C. The G-Ni/Pd was also stable and reusable, providing 98% conversion after the 5th catalytic run without showing any noticeable Ni/Pd composition change. The G-Ni/Pd structure reported in this paper combines both the efficiency of a homogeneous catalyst and the durability of a heterogeneous catalyst, and is promising catalyst candidate for various Pd-based catalytic applications. Open image in new window

We have demonstrated a facile sonication method to exfoliate graphite into few layer graphene with a high concentration of 1.3 mg/mL in oleic acid (OLA). The exfoliations of natural graphite in oleylamine (OA) and trioctylphosphine (TOP) are investigated as a comparison. The few layer graphene dispersion in OLA and the graphite nanoparticles in OA are confirmed by transmission electron microscopy (TEM) observation. The exfoliated graphene dispersion in OLA (OLA-G) and graphite dispersion in OA (OA-G) are fabricated into a film on the FTO substrate by the doctor-blading method. The morphology and catalytic activity in the redox couple regeneration of all the graphite films are examined by field emission scanning electron microscopy and cyclic voltammograms. The OLA-G films on FTO glass with few layer graphene flakes shows better catalytic activity than the OA-G films. The energy conversion efficiency of the cell with the OLA-G film as counter electrode reached 3.56%, which is 70% of dye-sensitized solar cell (DSSC) with the sputtering-Pt counter electrode under the same experimental condition.

We report a simple and rapid route for synthesis of CdSe quantum dots at low temperature of 150°C by using the paraffin oil as a solvent in place of the conventional trioctylphosphine and trioctylphosphine oxide. The CdSe QDs were synthesized as a function of the growth temperature. UV-vis and PL data show a narrow emission peak at 552 nm with absorption peak of 533 nm, implying a uniform size distribution. The CdSe QDs reveal large blue-shifts in both UV-vis and PL data under the low temperature conditions, due to the quantum confinement effect depending on the smaller particle size.

We demonstrate an organic synthesis to fabricate hydrophobic core/shell CdSe/Cd1−x Zn x S quantum dots (QDs) with tunable photoluminescence (PL) between green and red at relatively low temperature using trioctylphosphine S reacted directly with cadmium and zinc acetate. A seeded growth strategy was used for preparing large CdSe cores. Large CdSe cores revealed a rod-like morphology while small one exhibited a spherical shape. Being coated with a Cd1−x Zn x S shell on spherical CdSe cores with an average size of 3.9 nm in diameter, core/shell QDs exhibited a cubic morphology (a length of 5 nm). In contrast, the core/shell QDs created using a small core (3.3 nm in diameter) show a spherical morphology. Namely, the anisotropic aggregation behavior of CdS monomers on CdSe cores occurs when the rod-like core is coated with a Cd1−x Zn x S shell. CdS interlayer plays an important role for such morphology evolution because all CdSe cores with a pure ZnS shell exhibited a spherical morphology. The PL properties of CdSe/Cd1−x Zn x S core/shell QDs depended strongly on the size and morphology of the cores. The QDs revealed a narrow and tunable PL spectrum. It is believed that this facile strategy can be extended to synthesize other core–shell QDs at low temperature.

High-quality CdE (E = Te, TexSe1−x, Se) nanocrystals were synthesized at relatively low temperatures (180–200 °C) by the utilization of one-pot method without the use of pyrophoric reagents and alkylamines. Te dispersed in trioctylphosphine oxide (TOPO) and Se dissolved in paraffin oil were used as the chalcogen precursors, in which the use of any air-sensitive, toxic, and expensive starting materials such as trioctylphosphine (TOP) and tributylphosphine (TBP) was eliminated. Structural and optical characterizations demonstrated that high quality CdE nanocrystals were synthesized. The total synthesis cost can be saved as much as 60% when comparing with the widely used traditional TOP/TBP related methods. Also this is the first time to synthesize CdTe and CdTexSe1−x nanocrystals with one-pot method without TOP/TBP. More importantly, large scale synthesis of about 2–3 g of high quality CdE nanocrystal in one reaction was successfully conducted using this method, which is very attractive for the industrial applications of semiconductor nanocrystals.

Recent advances in the field of nanoscience have enabled the preparation of high-surface-area supported catalysts with precise control over the individual structural components. As such, a range of factors that affect the catalytic reactivity, such as the size, shape, and composition of the nanoparticles (NPs), have been identified. Herein, high-surface-area model catalysts that were based on colloidal Pd NPs and a hexagonally ordered mesoporous carbon support were prepared and the impact of various organic capping agents for the Pd NPs on their catalytic activity towards Suzuki coupling reactions was investigated. Colloidal Pd NPs (diameter: 3 nm) were synthesized with different organic capping agents, oleylamine (OA) and trioctylphosphine (TOP), and they were subsequently incorporated into the mesopores of CMK-3 mesoporous carbon to yield OA-Pd/CMK-3 and TOP-Pd/CMK-3 nanocatalysts, respectively. The OA-Pd/CMK-3 catalyst was treated with acetic acid to generate a supported catalyst with surfactant-free Pd NPs (OA-Pd/CMK-3-A). Structural characterization revealed that the Pd NPs were uniformly dispersed throughout the mesopores of the CMK-3 support and the particle size and crystallinity of the Pd NPs were preserved following the incorporation. All of the Pd/CMK-3 nanocatalysts exhibited higher activity than commercial activated carbon supported Pd catalysts in Suzuki coupling reactions. The catalytic activities of the three Pd/CMK-3 nanocatalysts were in the following order: OA-Pd/CMK-3-A>OA-Pd/CMK-3>TOP-Pd/CMK-3. This result suggested that the presence and type of surfactants had a significant effect on the catalytic activity. The OA-Pd/CMK-3-A catalyst also showed high activity for various substrates and good recycling ability in Suzuki coupling reactions.

This work aimed to study cobalt nanoparticles (Co-NPs) preparation using three different methods in order to evaluate the effect of synthesis variables that can influence the nanoparticle size distribution and particle shape. The synthesised nanoparticles were characterised by Transmission Electron Microscopy. The first synthesis employed decomposition of Co2(CO)8, at high temperatures. This procedure resulted in spherical nanoparticles with low size distribution. The size of Co-NPs could be tuned by modification of precursor/surfactant, nevertheless the stirring and injection time influenced the size distribution. Using polyol process, at high temperatures, it was produced undefined-shape nanoparticles. This result suggests that the solution composition, i.e. the amount of trioctylphosphine and oleic acid was not suitable to control both size and shape of nanoparticles. Finally, the method based on reduction with NaBH4 resulted spherical nanoparticles with tiny sizes, indicating that in this case a varia...

High quality PbSe and PbTe nanocrystals were synthesized with non-injection one-pot method which could be scale up easily. The use of traditional dangerous pyrophoric trioctylphosphine (TOP) and tributylphosphine (TBP) reagents was avoided. The crystal size was controlled by the reaction time and temperature, and the shape (sphere and cube) was controlled by the use of different combinations of surfactants. X-ray diffraction (XRD) and selective area electron diffraction (SAED) characterizations demonstrated the rock salt cubic structures; the transition electron microscopy (TEM) images show narrow size distributions of as-synthesized PbSe and PbTe nanocrystals. The uniform size of as-synthesized nanocrystals promoted the self-assemble of PbSe and PbTe nanocrystals into ordered superstructures.

The solvent extraction and stripping of titanium(Ⅳ) from acidic chloride solutions by trioctylphosphine oxide（TOPO） in kerosene has been investigated. The solvent extraction results demonstrate that the extracted titanium is present as TiCl4.2TOPO. The kinetics of the extraction process is very fast, since the equilibrium is reached in 5 min. In addition, the extraction of titanium (Ⅳ) increases with the total chloride concentration in the aqueous phase, as well as with the extractant concentration in the organic phase. The loading capacity of TOPO for titanium (Ⅳ) is 4.60g/100g TOPO. The stripping results show that when the O/A phase radio changing from 1 to 10, titanium (Ⅳ) is completely stripped from the mental loaded organic phase of TOPO with 1 mol dm-3 hydrochloric acid. Thus titanium (Ⅳ) can be enriched to tenfold concentration by the stripping.

A one-pot synthesis of large size and high quality AuAg alloy nanoparticles (NPs) with well controlled compositions via hot organic media is demonstrated. Amid the synthesis, complexation between trioctylphosphine (TOP) and metal precursors is found, which slows down the rate of nucleation and leads to the growth of large-size AuAg nanoalloys. The wavelength and relative intensities of the resulting plasmon bands are readily fine-tuned during the synthetic process using different Au/Ag precursors molar ratios. In the polymer solar cells, a key step in achieving high efficiency is the utilization of 1% Au11Ag89 alloy NPs embedded in the active layer to promote the power conversion efficiency (PCE) up to 4.73%, which outperforms the reference device based on the control standard device of poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PC61BM) under identical conditions. Corresponding increases in short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and incident photon-to-current efficiency (IPCE) enable 31% PCE improvement due to the enhancement of the light-trapping and the improvement of charge transport in the active layer. The findings advance the fundamental understanding and point to the superiority of Au11Ag89 nanoalloys as a promising metallic additive over Au, Ag, and Au28Ag72 alloy NPs to boost the solar cell performance.

Large-scale synthesis of high quality PbSe nanocrystals was conducted with the one-pot method. By this “greener” synthesis route, the use of traditional dangerous pyrophoric trioctylphosphine (TOP) and tributylphosphine (TBP) reagents was avoided. The crystal size and shape were controlled by the reaction time, reaction temperature, and the use of different combinations of surfactants. X-ray diffraction (XRD) and transition electron microscopy (TEM) were used to characterize as-synthesized nanocrystals and demonstrated the rock salt cubic structures and narrow size distributions. More than 3 g of high quality PbSe nanocrystals were synthesized in one reaction by this large-scale one-pot method. The uniform size of as-synthesized nanocrystals promoted the self-assembly of PbSe nanocrystals into large-area ordered superstructures.

The hydrophilization of CdSe quantum dots (QDs) obtained by a high-temperature method has been studied. For this purpose, the particles stabilized by hydrophobic shells of trioctylphosphine and trioctylphosphine oxide were additionally covered with molecules of hexadecyltrimethylammonium bromide, which caused the formation of a secondary hydrophilic shell around the particles. As a result, the luminescence efficiency of QDs after such hydrophilization was not only not reduced, as is often observed for other methods, but even increased in some cases. A possible mechanism for the observed phenomenon is discussed.

We demonstrate molecular control of nanoscale composition, alloying, and morphology (aspect ratio) in CdS-CdSe nanocrystal dots and rods by modulating the chemical reactivity of phosphine-chalcogenide precursors. Specific molecular precursors studied were sulfides and selenides of triphenylphosphite (TPP), diphenylpropylphosphine (DPP), tributylphosphine (TBP), trioctylphosphine (TOP), and hexaethylphosphorustriamide (HPT). Computational (DFT), NMR ((31)P and (77)Se), and high-temperature crossover studies unambiguously confirm a chemical bonding interaction between phosphorus and chalcogen atoms in all precursors. Phosphine−chalcogenide precursor reactivity increases in the order: HPTETOPETBPEDPPETPPE (E = SSe). For a given phosphine, the selenide is always more reactive than the sulfide. CdS(1-x)Se(x) quantum dots were synthesized via single injection of a R(3)PS-R(3)PSe mixture to cadmium oleate at 250 °C. X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV/Vis and PL optical spectroscopy reveal that relative R(3)PS and R(3)PSe reactivity dictates CdS(1-x)Se(x) dot chalcogen content and the extent of radial alloying (alloys vs core/shells). CdS, CdSe, and CdS(1-x)Se(x) quantum rods were synthesized by injection of a single R(3)PE (E = S or Se) precursor or a R(3)PS-R(3)PSe mixture to cadmium-phosphonate at 320 or 250 °C. XRD and TEM reveal that the length-to-diameter aspect ratio of CdS and CdSe nanorods is inversely proportional to R(3)PE precursor reactivity. Purposely matching or mismatching R(3)PS-R(3)PSe precursor reactivity leads to CdS(1-x)Se(x) nanorods without or with axial composition gradients, respectively. We expect these observations will lead to scalable and highly predictable "bottom-up" programmed syntheses of finely heterostructured nanomaterials with well-defined architectures and properties that are tailored for precise applications [corrected].

We show with the aid of first-principles electronic structure calculations that suitable choice of the capping ligands may be an important control parameter for crystal structure engineering of nanoparticles. Our calculations on CdS nanocrystals reveal that the binding energy of model trioctylphosphine molecules on the (001) facets of zincblende nanocrystals is larger compared to that on wurtzite facets. Similarly, the binding energy of model cis-oleic acid is found to be dominant for the (1010) facets of wurtzite structure. As a consequence, trioctylphosphine as a capping agent stabilizes the zincblende structure while cis-oleic acid stabilizes the wurtzite phase by influencing the surface energy, which has a sizable contribution to the energetics of a nanocrystal. Our detailed analysis suggests that the binding of molecules on the nanocrystalline facets depends on the surface topology of the facets, the coordination of the surface atoms where the capping molecule is likely to attach, and the conformati...

We present a low-temperature (68–70 °C) synthesis of green light-emitting, trioctylphosphine oxide-capped magic-sized CdSe nanoclusters from the reaction of trioctylphosphine oxide–cadmium acetate precursors with trioctylphosphine selenide. We observed continuous growth of these magic-sized nanoclusters, which displayed a first absorption peak at 422 nm and broad luminescence covering the entire visible region. The diameter of the nanoclusters determined by transmission electron microscopic measurement was ∼1.8 nm. Powder X-ray diffraction analysis showed a sharp peak at low angle (2θ = 5.3°), confirming the formation of ultrasmall, magic-sized nanoclusters. The nanocluster formation was also studied using different purities of trioctylphosphine oxide. The synthetic protocol was extended to the preparation of oleylamine-, ethylphosphonic acid-, lauric acid-, and trioctylamine-stabilized magic-sized CdSe nanoclusters. Importantly, the investigation showed that the nature of the cadmium precursors plays a c...

A chemical passivation strategy to improve durability in GaAs solar cells is described. Trioctylphosphine sulfide (TOP:S) is identified among a promising new class of surfactants for enhanced performance and longevity of GaAs cells. Light-beam induced current measurements (LBIC) and other studies show treatment with TOP:S mitigates efficiency losses at unpassivated sidewalls and induced fractures.

This Communication describes the synthesis of highly monodispersed 12 nm nickel nanocubes. The cubic shape was achieved by using trioctylphosphine and hexadecylamine surfactants under a reducing hydrogen atmosphere to favor thermodynamic growth and the stabilization of {100} facets. Varying the metal precursor to trioctylphosphine ratio was found to alter the nanoparticle size and shape from 5 nm spherical nanoparticles to 12 nm nanocubes. High-resolution transmission electron microscopy showed that the nanocubes are protected from further oxidation by a 1 nm NiO shell. Synchrotron-based X-ray diffraction techniques showed the nickel nanocubes order into [100] aligned arrays. Magnetic studies showed the nickel nanocubes have over 4 times enhancement in magnetic saturation compared to spherical superparamagnetic nickel nanoparticles.

Nearly all reported approaches for synthesis of high quality CdSe nanocrystals (NCs) involved two steps of preparation of Cd or Se stock solution in advance and then mixing the two reactants via hot-injection in high temperature. In this manuscript, Gram-scale CdSe multipod NCs were facilely synthesized in a noninjection route with the use of CdO and Se powder directly as reactants in paraffin reaction medium containing small amount of oleic acid and trioctylphosphine. The influence of various experimental variables, including reaction temperature, nature and amount of surfactants, Cd-to-Se ratio, and the nature of reactants, on the morphology of the obtained CdSe NCs have been systematically investigated. After deposition of ZnS shell around the CdSe multipod NCs, the PL QY of the obtained CdSe/ZnS can be up to 85%. The reported noninjection preparation approach can satisfy the requirement of industrial production bearing the advantage of low-cost, reproducible, and scalable. Furthermore, this facile noninjection strategy provides a versatile route to large-scale preparation of other semiconductor NCs with multipod or other morphologies.

Hierarchical, nanostructured nickel phosphide (h-Ni2P) spheres are synthesized by a one-pot reaction from an organic-phase mixture of nickel acetylacetonate, trioctylphosphine, tri-n-octylamine, and oleylamine (OAm). OAm is used as a surfactant to modify the surface morphology of Ni2P spheres. The h-Ni2P spheres are composed of ordered nanoparticles with 5–10 nm sizes and filled by amorphous carbon. The hierarchical structure can greatly increase the contact area between Ni2P and electrolyte, which provides more sites for Li+ accommodation, shortens the diffusion length of Li+, and enhances the reactivity of the electrode reaction. Also, the amorphous carbon and the hierarchical Ni2P nanostructures can buffer volume expansion and thus increase the electrode stability during cycling. In the context of storage behavior, the h-Ni2P electrode exhibits high capacity as well as Coulombic efficiency. After 50 cycles, the reversible capacity of h-Ni2P spheres is 365.3 mA h g–1 at 0.5 C and 257.8 mA h g–1 at 1 C, ...

We have synthesized CdSe nanocrystals (NCs) possessing a trioctylphosphine surface passivation layer and modified with amphiphilic molecules to form a surface bilayer. The NCs covered with single amphiphiles are not stable in aqueous solution, but a mixed amphiphilic system is shown to provide stability in solution over several months. The solutions of the modified NCs were characterized by UV-Vis absorbance, photoluminescence, and transmission electron microscopy. An electrophoretic study revealed two operational modes. The first relies on the enrichment of NCs using a micellar plug as a tool. The accumulation of NCs at the plug-electrolyte buffer interface results in a sharp peak. By controlling the electrophoretic conditions, nanocrystals were forced to exit a micellar plug into an electrolyte buffer. We conclude that a system consisting of modified nanocrystals and a micellar plug can act as a mixed pseudomicellar system, where modified nanocrystals play the role of pseudomicelles. Figure Electrophoretic focusing of amphiphile coated CdSe nanocrystals using a micellar plug. Electronic supplementary material The online version of this article (doi:10.1007/s00604-011-0727-8) contains supplementary material, which is available to authorized users.

The hot-injection approach has been intensively studied for the synthesis of nanocrystals formed in one-stage nucleation and growth. In the present study, we evaluated the application of hot injection in the preparation of hexagonal-phase NaYF4:Yb,Er nanocrystals, which is different in that it contains two stages: formation of cubic phase and consequent hexagonal phase. We found that when oleylamine was used as both solvent and ligand, the injecting temperature dictates the nucleation rate of cubic phase. Comparing with the classical heating-up approach, the phase transformation was accelerated. Following the same mechanism, in the mixed solvent of oleic acid (OA), trioctylphosphine (TOP), and octadecene, the size and shape of nanocrystals can be simultaneously adjusted. Especially, continuous change of aspect ratio of rodlike hexagonal-phase NaYF4:Yb,Er nanocrystals was observed and was ascribed to the kinetic balance between OA-TOP coupling and the phase transformation. Our results showed that kinetical...

Highly luminescent CdSe/Cd x Zn 1 − x S core/shell quantum dots (QDs) have been fabricated by a facile environmentally friendly organic route. The spherical cores and core/shell QDs were created by using Cd(AC) 2 ·2H 2 O, Zn(AC) 2 , oleic acid, trioctylphosphine (TOP), Se, S, and trioctylamine. The preparative condition such as reaction time (2–6 min), temperature (from 290 to 310 °C), and feed rate of TOPSe (0.3–2 mL/min) creates various sizes of the cores with photoluminescence (PL) wavelengths between 570 and 618 nm. Spherical CdSe cores were coated with a Cd x Zn 1 − x S shell via a single coating step by using different growth kinetics of CdS and ZnS at 300 °C. The CdSe/Cd x Zn 1 − x S core/shell QDs exhibited a significant red shift of PL peaks (up to 646 nm) from the initial PL of CdSe cores with much improved PL efficiency above 40% when the shell growth. By changing the size of the core and the thickness of the shell, the emission colors of the obtained core/shell QDs can be tuned between green and red.

Infrared-to-visible rare earth doped upconversion phosphors that convert multiple photons of lower energy to higher energy photons offer a wide range of technological applications. The brightness (i.e., emission intensities) and energy efficiency of phosphors are important performance characteristics that determine which applications are appropriate. Optical efficiency can be used as a measure of the upconversion emission performance of these rare earth doped phosphors. In this work, hexagonal-phase NaYF(4):Yb-Er was synthesized using the hydrothermal method in the presence of surfactants like trioctylphosphine, polyethylene glycol monooleate, and polyvinylpyrrolidone. The upconversion emission optical efficiencies of NaYF(4):Yb-Er were measured to quantify and evaluate the effects of surface coatings and accurately reflect the brightness and energy efficiency of these phosphors. Polyvinylpyrrolidone-modified NaYF(4):Yb-Er particles were found to be ~5 times more efficient and brighter than the unmodified particles. The difference in efficiency was attributed to reduced reflectance losses at the particle-air interface via refractive index mismatch reduction between the core NaYF(4):Yb-Er particles and air using polyvinylpyrrolidone as a surfactant.

Tin sulfide (SnS) particles were synthesized by thermal decomposition of tin acetate in a mixed solution of 1-dodecanethiol, one of coordinating solvents such as trioctylphosphine and oleylamine, and 1-octadecene as a noncoordinating solvent at 280 °C for 2 h. The morphology of the obtained SnS particles was determined by transmission electron microscopy. Needlelike SnS particles were obtained by using trioctylphosphine as a coordinating solvent. On the other hand, platelike SnS particles were obtained by using oleylamine. The SnS particles were formed by diffusion of sulfur derived from 1-dodecanethiol into Sn particles. In addition, the aspect ratio of needlelike SnS particles was affected by the amount of 1-dodecanethiol as a sulfur source. The all-solid-state cells using SnS particles with the different morphology as an active material were fabricated. The initial discharge capacity of the all-solid-state cell using needlelike SnS particles as an active material was ca. 1000 mAh g–1, which was larger ...

A detailed protocol for the large-scale synthesis of carbohydrate and dihydrolipoic acid (DHLA)-coated CdSe/ZnS and CdTe/ZnS nanoparticles using continuous flow reactors is described here. Three continuous flow microreaction systems, operating at three different temperatures, are used for the synthesis of mannose-, galactose- or DHLA-functionalized quantum dots (QDs). In the first step of synthesis, the CdSe and CdTe nanoparticles are prepared. The size and spectral properties of the CdSe core of the nanoparticles are controlled by adjustment of the residence time and the temperature. As a second step, the zinc sulfide capping under homogenous conditions is carried out at a substantially lower temperature than is required for nanoparticle growth in batch processes. Finally, the trioctylphosphine/oleic acid ligand is effectively replaced with either carbohydrate PEG-thiol moieties or DHLA at 60 °C. This new protocol allows the synthesis of biologically active fluorescent QDs in 4 d.

Surface effects significantly influence the functionality of semiconductor nanocrystals. High quality nanocrystals can be achieved with good control of surface passivation by various hydrophobic ligands. In this work, the chemistry between CdSe quantum dots and common surface capping ligands is investigated using density functional theory (DFT). We discuss the electronic structures and optical properties of small CdSe clusters controlled by their size of particle, self-organization, capping ligands, and positive charges. The chosen model ligands reproduce good structural and energetic description of the interactions between the ligands and quantum dots. In order to capture the chemical nature and energetics of the interactions between the capping ligands and CdSe quantum dots, we found that PMe3 is needed to adequately model trioctylphosphine (TOP), NH3 is sufficient for amines, while OPH2Me could be used to model trioctylphosphine oxide. The relative binding interaction strength between ligands was found to decrease in order Cd–O > Cd–N > Cd–P with average binding energy per ligand being −25 kcal/mol for OPH2Me, −20 kcal/mol for NH3 and −10 kcal/mol for PMe3. Charges on studied stoichiometric clusters were found to have a significant effect on their structures, binding energies, and optical properties.

Colloidal cadmium telluride (CdTe) quantum dots (QDs) and their nanoparticles have been synthesized by one pot sonochemical reactions under multibubble sonoluminescence (MBSL) conditions, which are quite mild and facile compared to other typical high temperature solution-based methods. For a typical reaction, and tellurium powder with hexadecylamine and trioctylphosphine/trioctylphosphineoxide (TOP/TOPO) as a dispersant were sonicated in toluene solvent at 20 KHz and a power of 220W for 5-40 min at 60 . The sizes of CdTe particles, in a very wide size range from 2 nm-30 , were controllable by varying the sonicating and thermal heating conditions. The prepared CdTe QDs show different colors from pale yellow to dark brown and corresponding photoluminescence properties due mainly to the quantum confinement effect. The CdTe nanoparticles of about 20 nm in average were found to have band gap of 1.53 eV, which is the most optimally matched band gap to solar spectrum.

We exploit the synthesis of CdSe core and CdSe/CdxZn1–xS core–shell quantum dots (QDs) with spherical and rod morphologies through a controlled core formation and single coating step by using different growth kinetics of CdS and ZnS. The size and morphology of CdSe cores depended strongly on the injection speed of trioctylphosphine selenium (TOPSe), reaction temperature, and time. The cores with spherical morphology exhibited tunable photoluminescence (PL) wavelength from 544 to 623 nm. CdSe cores with rod morphology and a PL peak wavelength of 623 nm were prepared when TOPSe was injected slowly. The molar ratio of Cd/Zn upon preparation was adjusted for investigating the effect of the CdxZn1–xS shell on the properties of the resulting core–shell QDs. The coated QDs exhibited a controlled red shift from the initial PL of CdSe cores with much improved PL efficiency (a maximum value of 89%). CdSe/CdxZn1–xS core–shell QDs prepared by using those rod cores exhibited a PL peak wavelength of 652 nm and a PL eff...

High-quality Zn3P2 nanowires are synthesized at a temperature as low as 350 °C using Zn foil and trioctylphosphine by chemical reflux method. Scanning electron microscopy and transmission electron microscopy (TEM) images show their diameters vary from ∼15 to 70 nm. Energy dispersive x-ray spectroscopy and nanobeam electron diffraction patterns in combination with structure factor simulation reveal that the nanowires have tetragonal α-Zn3P2 structure. Based on high-resolution TEM images and their fast Fourier transform patterns, Zn3P2 nanowires are considered to grow on a vicinity of the possibly highest surface energy plane of (101) with a growth direction parallel to [101].

Structural phase-controlled formation of binary Co(2)P and CoP nanocrystals is achieved by reacting cobalt(II) oleate with trioctylphosphine. In the absence of oleylamine, Co(2)P nanowires are formed at both 290 and 320 °C. In the presence of oleylamine, Co(2)P nanorods are formed at 290 °C, and CoP nanorods are formed at 320 °C. With the simultaneous reaction of iron(III) oleate and cobalt(II) oleate with trioctylphosphine in the presence of oleylamine, ternary Co(2)P-type cobalt-iron phosphide nanostructures are produced at both 290 and 320 °C, corresponding to rice-shaped Co(1.5)Fe(0.5)P nanorods and split Co(1.7)Fe(0.3)P nanostructures, respectively. The controlled incorporation of iron into cobalt phosphide can alter the magnetic properties from paramagnetic binary Co(2)P to ferromagnetic Co(2)P-type ternary cobalt-iron phosphide nanostructures. Meanwhile, the time-dependent morphological evolution from small nanodots/nanorods, through seeded growth to unique split nanostructures is demonstrated in one-pot reaction at 320 °C.

We prove that CdS nanocrystals can be thermodynamically stabilized in both wurtzite and zinc-blende crystallographic phases at will, just by the proper choice of the capping ligand. As a striking demonstration of this, the largest CdS nanocrystals (similar to 15 nm diameter) ever formed with the zinc-blende structure have been synthesized at a high reaction temperature of 310 degrees C, in contrast to previous reports suggesting the formation of zinc-blende CdS only in the small size limit (< 4.5 nm) or at a lower reaction temperature (

Modulation of Pd nanoparticle (NP) crystallinity is achieved by switching the surfactants of different binding strengths. Pd NPs synthesized in the presence of weak binding surfactants such as oleylamine possess polyhedral shapes and a polycrystalline nature. When oleylamine is substituted by trioctylphosphine, a much stronger binding surfactant, the particles become spherical and their crystallinity decreases significantly. Moreover, the Pd NPs reconvert their polycrystalline structure when the surfactant is switched back to oleylamine. Through control experiments and molecular dynamics simulation, we propose that this unusual nanocrystallinity transition induced by surfactant exchange was resulted from a counterbalance between the surfactant binding energy and the nanocrystal adhesive energy. The findings represent a novel postsynthetic approach to tailoring the structure and corresponding functional performance of nanomaterials.

The condensation of linear diamine and dialdehyde subcomponents around copper(I) templates in the presence of bulky trioctylphosphine ancillary ligands gave a linear, conjugated polymeric material in DMSO solution. This polymer solution was observed to undergo sol-to-gel transition as the temperature was raised to 140 °C, in contrast with the behavior of most gel-forming polymers, which do so upon cooling. We attribute the sol-to-gel transition to the formation of Cu(I)N(4) cross-links as the equilibria 2[Cu(I)N(2)P(2)] ⇄ [Cu(I)N(4)] + [CuP(n)](+) + (4 - n)P favor the right-hand side at higher temperatures. The material was also observed to exhibit thermochromism and photoluminescence, with the color and intensity of both absorption and emission exhibiting temperature dependence. This material thus responds predictably to combinations of stimuli (heat, light, mechanical shear) in an interconnected way, as is required to generate complex function.

The coating makes the wire bundle: High-quality free-standing copper nanowires have been successfully produced by disproportionation of Cu(+) in oleylamine. This provides an effective way to prepare high-quality copper nanowires, but also enriches synthetic routes to other nanostructures. These copper nanowires can self-assemble by surface ligand exchange of oleylamine with trioctylphosphine.