Short Nanorods Research Articles

Insights into the enhanced photoelectrochemical performance of hydrothermally controlled hematite nanostructures for proficient solar water oxidation.

In this paper, we focus on the controlled growth mechanism of α-Fe2O3 nanostructures via the hydrothermal method. The field emission scanning electron microscopy (FESEM) results reveal that at a lower hydrothermal time, the initial nucleation involves the formation of short and thin β-FeOOH nanorods. The subsequent increase in the hydrothermal time leads β-FeOOH to form thicker and longer nanorods. However, high-temperature quenching (HTQ) at 800 °C for 10 min causes the conversion of akaganeite to the hematite phase and activation of hematite by Sn4+ diffusion from a FTO substrate. Sn4+ diffusion from the FTO substrate to the hematite nanostructure was elaborated by X-ray photoelectron spectroscopy (XPS). An α-Fe2O3 nanorod photoanode prepared by a hydrothermal reaction for 3 h and HTQ exhibits the highest photocurrent density of 1.04 mA cm-2. The excellent photoelectrochemical performance could be ascribed to the synergistic effect of the optimum growth of α-Fe2O3 nanorod arrays and Sn4+ diffusion. Intensity modulated photovoltage spectroscopy (IMVS) studies revealed that the α-Fe2O3 photoanodes prepared at 3 h and HTQ exhibited a long electron lifetime (132.69 ms), and contribute to the enhanced PEC performance. The results confirmed that the controlled growth of the β-FeOOH nanorods, as well as Sn4+ diffusion, played a key role in charge transfer during the photoelectrochemical application. The charge transfer mechanisms in α-Fe2O3 nanostructure photoanodes prepared at different hydrothermal times and high-temperature quenching are also investigated.

Silver nanoparticles with low cytotoxicity: controlled synthesis and surface modification with histidine

Due to the controlled release of Ag+, silver nanoparticles (AgNPs) not only display excellent anticancer activity but also possess cytotoxicity on normal cells. Up to now, no efficient method has been found to eliminate the side effect. In this study, AgNPs with different morphologies were synthesized and some main factors, i.e., the seed amount, CTAB concentration and temperature were discussed. Histidine (His) was applied to modify three kinds of AgNPs (near nanospheres, short nanorods and long nanorods) prepared by the above controlled synthesis, and the bioactivity of the modified AgNPs on cancer and normal cells was investigated. The results showed that the morphology and particle size of AgNPs had strong dependency on the quantity of seeds and reaction temperature except for CTAB concentration. IR spectra showed that His molecules had linked to AgNPs by coordination between AgNPs and C–N group of the imidazolyl in His. The bioactivity experiments in vitro showed that the cytotoxicity of His-modified AgNPs on HL7702 cells was effectively reduced and the anti-tumor activity against MCF-7 cells was not influenced obviously. The results supported that the His-modified AgNPs possess less cytotoxicity and higher targeting anticancer activity and thus the silver nanomaterials modified by His displayed potential applications for cancer therapies. We also suggested that the possible mechanism on the reduction of the cytotoxicity was that His-modified AgNPs could target cancer cells to decrease the cytotoxicity but affect a little on the viability of normal cells.

Ultrafast Synthesis and Coating of High-Quality β-NaYF4:Yb3+,Ln3+ Short Nanorods.

An ultrafast route to prepare up-converting single β-phase NaYF4:Yb3+,Ln3+ (Ln: Er, Tm, or Tb) short nanorods (UCNRs) of high quality was developed. This new procedure affords reactive-surface nanorods that are easily coated by direct injection of suitable capping ligands. Thus highly crystalline nanorods with excellent UC fluorescence and good solvent-selective dispersion are obtained, which represents a significant advance in the field and enlarges their use for biomedical and other technological applications. Unlike other methodologies, the short reaction time provides a kinetic control over crystallization processes, and the β-phase and rod morphology is preserved regardless of the optically active Ln3+ ion. The UC emission was finely tuned by using the most popular Yb3+/Tm3+ and Yb3+/Er3+ pairs. More importantly, UCNRs doped with the unusual Yb3+/Tb3+ pair, with no ladder-like energy levels, provided a nice emission upon near-infrared excitation, which constitutes the first example of phonon-assisted cooperative sensitization to date in pure β-NaYF4 nanocrystals.

Peptide Self-Assembled Nanostructures with Distinct Morphologies and Properties Fabricated by Molecular Design.

Six surfactant-like peptides with the same amino acid composition but different primary sequences are designed, including G3A3V3I3K3, K3I3V3A3G3, I3V3A3G3K3, K3G3A3V3I3, V3G3I3A3K3, and K3A3I3G3V3. These peptides form antiparallel β-sheets during self-assembly. Because the constituent residues have different side chain size and hydrophobicity, sequence changes adjust group distribution and hydrophobicity on the two sides of a given β-sheet. This consequently tunes the binding energy of the side-to-side pairing conformations and leads to different self-assembled structures. G3A3V3I3K3 and K3I3V3A3G3 form short nanorods with diameters of 8.5 ± 1.0 nm and lengths <150 nm. I3V3A3G3K3 and K3G3A3V3I3 form nanosheets with heights of 4.0 ± 0.5 nm and limited lengths and widths. V3G3I3A3K3 and K3A3I3G3V3 form long fibrils with diameters of 7.0 ± 1.0 nm and lengths of micrometer scale. These nanostructures exhibit different capacity in encapsulating insoluble hydrophobic drug molecules and delivering them into the cells. The nanosheets of I3V3A3G3K3 and K3G3A3V3I3 can encapsulate both nile red and doxorubicin molecules to an extent of up to 17-23% in mole ratio. Moreover, the shape and size of the nanostructures affect the drug delivery into cells greatly, with the nanosheets and short rods exhibiting higher efficiency than the long fibrils. The study provides new insights into programmed peptide self-assembly toward specific functionalities.

Observation of Morphology and Structure Evolution during Gelation of a Bis(Anhydrazide) Derivative.

A new bis(anhydrazide) derivative containing cyclohexyl terminal groups (compound 1) was synthesized, and its gelation process was investigated. Compound 1 showed both thermal-induced gelation (T-gel) and sonication-induced gelation (S-gel) in alcohols. We investigated the gelation process of compound 1 in ethanol by different techniques. It was demonstrated that gelator 1 in ethanol underwent a transition from a clear solution through a turbid suspension to an opaque gel. Scanning electron microscopy (SEM) observations indicated that the turbid suspension consisted of separated clew-like spheres, connected spheres, and short nanorods, whereas the opaque gel consisted of fibers or bundles of fiber networks. Molecules packed loosely into an unknown phase in the spheres, whereas they packed tightly into a hexagonal columnar phase with a = 1.62 nm in the fibers. Intermolecular H-bonding between -C═O and -N-H was revealed to be the driving force for gelation, and the strength of the H-bonding became stronger in the fibers than in the spheres. We propose that the gel of compound 1 in ethanol consisting of fibers is a stable phase compared to the turbid suspension consisting of spheres or short nanorods, which is considered to be metastable. The kinetics of gelation of gelator 1 in ethanol under sonication suggest that the gelation process is a two-stage kinetic pathway with fractal values of 1.27 and 0.84. Our study hence provides new insights into the formation of fibers and the structural evolution of the gelation process and can be exploited to achieve a detailed understanding of gels.

Influence of the sol gel synthesis parameters on the photoluminescence properties of ZnO nanoparticles

In this work, ZnO NPs were successfully synthesized by the sol–gel method without any organic additives or post annealing. The effect of the preparation process on the structural and optical properties of the resulting NPs was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The structural characterization demonstrated clearly that the NPs crystallize in pure ZnO würtzite structure without any other secondary phases. Furthermore, we show that it is possible to perform the control of the crystalline growth orientation of ZnO NPs, which is a key parameter when seeking to develop ZnO NPs with piezoelectric properties for nano-transducer applications. In fact, TEM observations show that the reduction of the NaOH flow changes the NPs shape from hexagonal NPS to short nanorods grown along the c-axis. The PL spectra of the obtained NPs excited at 280nm, present an UV emission centered at approximately 380nm with a slight shift when varying the synthesis temperature and/or the NaOH flow. Moreover, as the visible region (from 400 to 650nm) is concerned, it was shown that the increasing of the synthesis temperature affects strongly the kind of interstitial defects (Oi, Zni and VoZni) formed in ZnO nanostructures. However, the excitation at 320nm revealed a broad deep-level emission for all the samples that can be deconvoluted into two Gaussian peaks centered at 514nm (P1) and 581nm (P2). These last results have been discussed in the light of a physical mechanism based on the Schottky barrier.

Synthesis of CuO/SBA-15 nanocomposite in ternary system of CO2, inorganic salt and co-solvent

Highly dispersed CuO nanoparticles were successfully synthesized within mesoporous silica in supercritical CO2 using inorganic Cu precursors. Co-solvent and deposition time were found to have significant influence on the metal loading and the morphology of the nanophase. The agglomerates of nanoparticle outside the SBA-15 channels were obtained, whose size were about 20–80nm, when ethanol, 1,3 propylene glycol and n-butyl alcohol were used as co-solvent, although the inorganic precursor has large solubility in them. When ethylene glycol was used as co-solvents, large amounts of continuous nanowires were found inside the SBA-15 channels. However, when the mixture of ethylene glycol and water were used as co-solvent, short nanorods or even nanoparticles were found instead. It indicates that the role of the co-solvent may have many aspects, such as enhancement of the precursor dissolution, change of the interaction between the precursor and the substrates and so on. In addition, it was found that a larger amount of co-solvent had negative effect on the metal loading, mainly due to the phase separation of the ternary system of supercritical CO2, co-solvent and inorganic precursors.

Size-controlled synthesis and morphology evolution of Nd 2 O 3 nano-powders using ionic liquid surfactant templates

A novel surfactant liquid template has been developed for the synthesis of monodisperse neodymia (Nd2O3) nanoparticles with various morphologies. The effects of surfactant concentration and type were studied in the preparation process. The precursors and Nd2O3 powders were determined by several analytic techniques such as XRD, TG/DSC, SEM and FTIR. The morphologies of products were indicated to be highly influenced by the added amount of N-(3-Cocoamidopropyl)-betaine (CAPB) or 1-tetradecyl-3-methylimidazolium chloride ([C14mim]Cl) ionic liquid (IL) surfactants. With the increase of CAPB concentration from 0 to 20 times of critical micelle concentration (CMC), the morphologies of Nd2O3 varied from short nanorods, nanoballs, irregular flakes, highly regular leaf-shaped nanoparticles to torispherical nanoparticles, and the phases of Nd2O3 mentioned above were all the same. However, the morphology of Nd2O3 prepared by adding [C14mim]Cl surfactant was quite different to that prepared with CAPB surfactant. A possible mechanism was proposed to explain the influence of surfactant concentration on the precipitation process. The surfactant formed different micelle structures, i.e., sphere micelle, lamellar micelle and liquid crystal micelle, as the liquid templates for guiding the precipitation reaction. The synthetic procedure was fairly simple and showed great promise for the application of some other IL surfactants to prepare nanoparticles, fabricating a variety of building blocks for assembling nanomaterials with novel structures and functionalities.

Fusion behaviour and mechanism of ultrafine Ag-Cu nanoparticles induced by electron beam irradiation

Understanding the thermal evolution mechanisms of metal nanoparticles (NPs) at the quantum-dot-scale is arrestive and meaningful for utilization of nanomaterials. Herein, an interesting fusion evolution phenomenon of Ag-Cu NPs induced by in-situ TEM high-energy electron beam illumination has been observed and investigated. It turned out that a rapid fusion process was in progress as reflected by the significant morphological change as the electron beam illumination time increased. The Ag-Cu NPs clusters tended to shrink their overall surface area along with the increase of sintering neck radii and decrease of neck curvature which was dominated by lattice diffusion mechanism. In addition, the necks among three Ag-Cu NPs continuously grew until the three particles became a short nanorod with a relatively uniform lateral diameter of about 20 nm after 300 sʹ illumination. It was also worthy of note that the smaller particles disappeared faster than bigger ones due to their highest surface energy.

Plasma-induced synthesis of Pt nanoparticles supported on TiO2 nanotubes for enhanced methanol electro-oxidation

A Pt/C/TiO2 nanotube composite catalyst was successfully prepared for enhanced methanol electro-oxidation. Pt nanoparticles with a particle size of 2nm were synthesized by plasma sputtering in water, and anatase TiO2 nanotubes with an inner diameter of approximately 100nm were prepared by a simple two-step anodization method and annealing process. Field-emission scanning electron microscopy images indicated that the different morphologies of TiO2 synthesized on the surface of Ti foils were dependent on the different anodization parameters. The electrochemical performance of Pt/C/TiO2 catalysts for methanol oxidation showed that TiO2 nanotubes were more suitable for use as Pt nanoparticle support materials than irregular TiO2 short nanorods due to their tubular morphology and better electronic conductivity. X-ray photoelectron spectroscopy characterization showed that the binding energies of the Pt 4f of the Pt/C/TiO2 nanotubes exhibited a slightly positive shift caused by the relatively strong interaction between Pt and the TiO2 nanotubes, which could mitigate the poisoning of the Pt catalyst by COads, and further enhance the electrocatalytic performance. Thus, the as-obtained Pt/C/TiO2 nanotubes composites may become a promising catalyst for methanol electro-oxidation.

Effect of different LaPO 4 supports on the catalytic performance of Rh 2 O 3 /LaPO 4 in N 2 O decomposition and CO oxidation

Abstract LaPO 4 has been used as a support to make supported catalysts in some investigations, but the effect of different LaPO 4 supports on the catalytic performance of supported catalysts has been rarely reported. In this work, conventional hexagonal LaPO 4 (LaPO 4 H) was prepared by precipitation, and hexagonal LaPO 4 nanowires (LaPO 4 HNW) was prepared by hydrothermal synthesis at 150 °C. Monoclinic LaPO 4 nanowires (LaPO 4 -MNW-220 and LaPO 4 -MNW-900) were prepared by hydrothermal synthesis at 220 °C or calcining LaPO 4 HNW at 900 °C. These samples were used to support Rh 2 O 3 via impregnation using Rh(NO 3 ) 3 as a precursor. The activities of these supported catalysts in N 2 O decomposition and CO oxidation follow the same sequence of Rh 2 O 3 / LaPO 4 HNW > Rh 2 O 3 / LaPO 4 H > Rh 2 O 3 / LaPO 4 -MNW-220 > Rh 2 O 3 / LaPO 4 -MNW-900, i.e. , two hexagonal LaPO 4 supports are better than two monoclinic LaPO 4 supports in making active catalysts, and hexagonal LaPO 4 nanowires are better than hexagonal LaPO 4 composed of nanoparticles and short nanorods. The most active catalyst has highly dispersed Rh 2 O 3 species interacting strongly with the support, more oxygen-adsorption capacity, and more basic sites.

The general synthesis and characterization of rare earth orthovanadate nanocrystals and their electrochemical applications

We report a novel, simple synthetic route to uniform and highly crystalline rare earth orthovanadate (LnVO4, Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, or Y) nanocrystals prepared through the reaction between Ln(III)-acetate and a vanadyl sulfate aqueous solution in xylene in the presence of surfactants. In the presented synthesis, vanadyl sulfate was introduced as a new vanadate source to control the reaction rate, thus leading to formation of highly crystalline LnVO4 nanocrystals in a mild reaction condition. By changing the Ln source from Ce to Er, the morphology of the LnVO4 nanocrystals could be easily controlled from long nanorods to short nanorods and nanodisks. The synthesized LnVO4 nanocrystals exhibited good cycling stability and a high rate capability at various current densities when used as electrode materials for Li-ion battery.

Peapod-like V2O3 nanorods encapsulated into carbon as binder-free and flexible electrodes in lithium-ion batteries

Abstract Designing and fabricating electrodes with excellent mechanical flexibility and superior electrochemical performance for high-performance lithium ion battery (LIBs) is challenging. Herein, ultralong peapod-like nanowires (NWs) composed of short vanadium sesquioxide nanorods (V 2 O 3 NRs) encapsulated with carbon are produced as high-performance anode materials. The freestanding and flexible film has a high capacity of 210 mAh g −1 at a current density of 0.1 C, and exhibits appreciable rate capability with 68% capacitance retention when the current density is increased from 0.1 to 1 C, and excellent long-term cycling stability without apparent capacity fading after 125 cycles, which is better then that of the active carbon mixed V 2 O 3 NRs and bare V 2 O 3 NRs. The outstanding electrochemical performance is attributed to proper accommodation of the volume expansion of the vanadium oxide in the carbon in the lithiation/delithiation process as well as the outer conductive three-dimensional (3D) carbon network. The formation mechanism of the peapod-like structure is investigated by thermogravimetric analysis connected to a mass spectrometer (MS). The ultralong peapod-like nanostructure overcomes the physical and chemical drawbacks of vanadium oxide and has large potential applicability for flexible energy-storage devices.

Antibacterial activity of silver nanoparticles with different morphologies as well as their possible antibacterial mechanism

Silver nanoparticles (AgNPs) have good antibacterial activity and their morphologies have important influence on their activity. The relationship between their bactericidal property and morphology has not been studied thoroughly. Silver triangular nanoplates have basic {111} surface, nanospheres and nanocubes mainly have {100} planes, and nanorods have {100} side surfaces and {111} end facets. It was said that {111} crystal plane of AgNPs may play a prime role in antibacterial progress. Moreover, the antibacterial activity of nanocubes is not very clear when compared to nanoparticles with other morphologies. In this paper, we studied the antibacterial activity of nanocubes and attempted to confirm whether nanoparticles with {111} crystal facet truly had stronger antibacterial activity than other nanoparticles. We prepared four kinds of AgNPs and found silver triangle nanoplates had the best antibacterial activity, while nanospheres, nanocubes and short nanorods showed similar efficacy. It may provide a reference for safe application of AgNPs with different morphologies in the medical field.

Nanorod-Based Supramolecular Nanocomposites: Effects of Nanorod Length

Nanorods (NRs) have unique anisotropic properties that are desirable for various applications. Block copolymer-based supramolecules present unique opportunities to control inter-rod ordering and macroscopic alignment of NRs to fully take advantage of their unique anisotropic properties. Here, we studied the effects of NR aspect ratio where the NR length is in the range of 20–180 nm on the assemblies of NRs in supramolecular framework. At a moderate loading (∼3 vol %), well-ordered assemblies of 37–90 nm NRs embedded in the supramolecular framework were formed. Shorter NRs (∼22 nm) coassemble with the supramolecule but were not well-ordered and displayed little orientational control within the microdomains. In contrast, longer NRs (∼180 nm) formed kinetically trapped states that restricted the formation of well-ordered coassemblies in NR/supramolecule blends. Additionally, the NRs are shown to be capable of kinetically trapping the system after normally reversible morphological transitions triggered by the...

Heterocyclic Bismuth(III) Dithiocarbamato Complexes as Single-Source Precursors for the Synthesis of Anisotropic Bi2 S3 Nanoparticles.

New complexes catena-(μ2 -nitrato-O,O')bis(piperidinedithiocarbamato)bismuth(III) (1) and tetrakis(μ-nitrato)tetrakis[bis(tetrahydroquinolinedithiocarbamato)bismuth(III)] (2) were synthesised and characterised by elemental analysis, FTIR spectroscopy and thermogravimetric analysis. The single-crystal X-ray structures of 1 and 2 were determined. The coordination numbers of the Bi(III) ion are 8 for 1 and ≥6 for 2 when the experimental electron density for the nominal 6s(2) lone pair of electrons is included. Both complexes were used as single-source precursors for the synthesis of dodecylamine-, hexadecylamine-, oleylamine and tri-n-octylphosphine oxide-capped Bi2 S3 nanoparticles at different temperatures. UV/Vis spectra showed a blueshift in the absorbance band edge characteristic of a quantum size effect. High-quality, crystalline, long and short Bi2 S3 nanorods were obtained depending on the thermolysis temperature, which was varied from 190 to 270 °C. A general trend of increasing particle breadth with increasing reaction temperature and increasing length of the carbon chain of the amine (capping agent) was observed. Powder XRD patterns revealed the orthorhombic crystal structure of Bi2 S3 .

Mechanism for the Cellular Uptake of Targeted Gold Nanorods of Defined Aspect Ratios.

Biomedical applications of non-spherical nanoparticles such as photothermal therapy and molecular imaging require their efficient intracellular delivery, yet reported details on their interactions with the cell remain inconsistent. Here, the effects of nanoparticle geometry and receptor targeting on the cellular uptake and intracellular trafficking are systematically explored by using C166 (mouse endothelial) cells and gold nanoparticles of four different aspect ratios (ARs) from 1 to 7. When coated with poly(ethylene glycol) strands, the cellular uptake of untargeted nanoparticles monotonically decreases with AR. Next, gold nanoparticles are functionalized with DNA oligonucleotides to target Class A scavenger receptors expressed by C166 cells. Intriguingly, cellular uptake is maximized at a particular AR: shorter nanorods (AR = 2) enter C166 cells more than nanospheres (AR = 1) and longer nanorods (AR = 4 or 7). Strikingly, long targeted nanorods align to the cell membrane in a near-parallel manner followed by rotating by ≈90° to enter the cell via a caveolae-mediated pathway. Upon cellular entry, targeted nanorods of all ARs predominantly traffic to the late endosome without progressing to the lysosome. The studies yield important materials design rules for drug delivery carriers based on targeted, anisotropic nanoparticles.

Hydrothermal synthesis of Co3O4 nanowire electrocatalysts for oxygen evolution reaction

Herein, we reported a well-controlled hydrothermal synthesis of Co3O4 nanowires using CoSO4 as a cobalt precursor and glycerol as a morphological directing agent. Scanning electron microscopy was employed to observe the growth of nanowires. As an important synthetic parameter, reaction time is spanned from 4 to 24 h, which played an important role in the morphology and properties of materials. When the reaction time was 4 h, the resulting Co3O4 nanoparticles assembled into some short nanorods. While increasing the reaction time, the nanorods grew into long nanowires with large aspect ratio, and then attached into bundles when the reaction time was extended up to 24 h. Electrochemical characterization shows that Co3O4 nanowires prepared by hydrothermal reaction for 12 h exhibited the highest catalytic activity for oxygen evolution reaction (OER) among all synthesized nanowires and nanoparticles using the similar method. The enhanced OER activity of the 12 h-prepared Co3O4 nanowires should be attributed to the increased electroactive surface area because observed from the cyclic voltammogram, the 12 h-prepared Co3O4 nanowires possessed the highest surface area among all tested samples. It was also illustrated that there existed a close correlation of the OER catalytic activity with the transition of oxidation state and the density of activity sites of the catalyst exposing to the electrolyte solution during the electrolysis. Though both Co3O4 nanowires and nanoparticles exhibited a considerable loss in OER activity during the stability testing, after polarization for 4 h at 1.7 V (versus a reversible hydrogen electrode), the Co3O4 nanowires still produced the higher catalytic current than that of the Co3O4 nanoparticles showing a slightly higher stability than the particles because of the nanowire structure.

Facile synthesis of S–Ag nanocomposites and Ag2S short nanorods by the interaction of sulfur with AgNO3 in PEG400

A facile, eco-friendly and inexpensive method to prepare Ag2S short nanorods and S–Ag nanocomposites using sublimed sulfur, AgNO3, PVP and PEG400 was studied. According to x-ray diffraction and scanning electron microscopy of the Ag2S, the products are highly crystalline and pure Ag2S nanorods with diameters of 70–160 nm and lengths of 200–360 nm. X-ray diffraction of the S–Ag nanocomposites shows that we obtained cubic Ag and S nanoparticles. Transmission electron microscopy shows that the molar ratio of PVP to Ag+ plays an important role in controlling the size and morphology of the S–Ag nanocomposites. When the molar ratio of PVP to Ag+ was 10:1, smaller sizes, better dispersibility and narrower distribution of S–Ag nanocomposites with diameters of 10–40 nm were obtained. The formation mechanism of the S–Ag nanocomposites was studied by designing a series of experiments using ultraviolet–visible measurement, and it was found that S nanoparticles are produced first and act as seed crystals; then Ag+ becomes Ag nanocrystals on the surfaces of the S nanoparticles by the reduction of PVP. PEG400 acts as a catalyzer, accelerating the reaction rate, and protects the S–Ag nanocomposites from reacting to produce Ag2S. The antimicrobial experiments show that the S–Ag nanocomposites have greater antimicrobial activity on Staphylococcus aureus, Aspergillus niger and blue mold than Ag nanoparticles.

Synthesis of WO3−x nanomaterials with controlled morphology and composition for highly efficient photocatalysis

Abstract