PubMed Journal Database | ACS nano 
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Showing PubMed Articles 1–25 of 1,300+ from ACS nano
Sequential and Site-Specific On-Surface Synthesis on a Bulk Insulator.
The bottom-up construction of functional devices from molecular building blocks offers great potential in tailoring materials properties and functionality with utmost control. An important step towards exploiting bottom-up construction for real-life applications is the creation of covalently bonded structures that provide sufficient stability as well as superior charge transport properties over reversibly linked self-assembled structures. On-surface synthesis has emerged as a promising strategy for fabricat...
Thin Porous Alumina Sheets as Supports for Stabilizing Gold Nanoparticles.
Thin porous alumina sheets have been synthesized using a lysine-assisted hydrothermal approach resulting in an extraordinary catalyst support that can stabilize Au nanoparticles at annealing temperatures up to 900 °C. Remarkably, the unique architecture of such an alumina with thin sheets (the average thickness ~15 nm and length 680 nm) and rough surface is beneficial to prevent gold nanoparticles from sintering. HRTEM observations clearly showed that the epitaxial growth between Au nanoparticles and alumi...
We herein report a new class of photonic crystals (PCs) with hierarchical structures, which are of color tunability over pH. The materials were fabricated through the deposition of polymethylacrylic acid (PMAA) onto a Morpho butterfly-wing template by using a surface bonding and polymerization route. The amine groups of chitosan in Morpho butterfly wings provide reaction sites for MAA monomer, resulting in hydrogen bonding between the template and MAA. Subsequent polymerization results in PMAA layers coatin...
CuInSe2, which is one of the highest efficiency thin-film solar cell active layer materials, has been an attractive target for nanocrystal synthesis and manipulation. Here, we report unprecedented, simultaneous control of the synthesis and self-assembly behavior of CuInSe2 nanocrystals. These nanocrystals are solution-processable, monodisperse tetragonal bipyramids that exhibit photoconductivity and self-assemble into crystallographically oriented thin films. Structural characterization indicates that these...
Room-Temperature Single-Electron Charging Detected by Electrostatic Force Microscopy.
We use atomic force microscopy to measure electron addition spectra of individual Au nanoparticles that exhibit Coulomb blockade at room temperature. The cantilever tip charges individual nanoparticles supported on an ultra-thin NaCl film via single-electron tunneling from the metal back electrode. The tunneling is detected by measuring frequency shift and damping of the oscillating cantilever. Finite element electrostatic calculations indicate that the total nanoparticle capacitance is dominated by mutual...
Nanodiamond nanofluids for enhanced thermal conductivity.
Deaggregation of oxidized ultradispersed diamond (UDD) in dimethylsulfoxide followed by reaction with glycidol monomer, purification via aqueous dialysis, and dispersion in ethylene glycol (EG) base fluid affords nanodiamond (ND)-poly(glycidol) polymer brush:EG nanofluids exhibiting 12% thermal conductivity enhancement at a ND loading of 0.9 vol %. Deaggregation of UDD in the presence of oleic acid/octane followed by dispersion in light mineral oil and evaporative removal of octane gives ND·oleic acid:mine...
Chiral "pinwheel" heterojunctions self-assembled from c60 and pentacene.
We demonstrate the self-assembly of C60 and pentacene (Pn) molecules into acceptor-donor heterostructures which are well-ordered and-despite the high degree of symmetry of the constituent molecules-chiral. Pn was deposited on Cu(111) to monolayer coverage, producing the random-tiling (R) phase as previously described. Atop R-phase Pn, postdeposited C60 molecules cause rearrangement of the Pn molecules into domains based on chiral supramolecular "pinwheels". These two molecules are the highest-symmetry achir...
Plasmonic excitation in metals has received great attention for light localization and control of light-matter interactions at the nanoscale with a plethora of applications in absorption enhancement, surface-enhanced Raman scattering, or biosensing. Electrically active plasmonic devices, which had remained underexplored, have recently become a growing field of interest. In this report we introduce a metal-insulator-semiconductor heterostructure for plasmo-electric energy conversion, a novel architecture to...
Nonvolatile Memory Cells Based on MoS2/Graphene Heterostructures.
Memory cells are an important building block of digital electronics. We combine here the unique electronic properties of semiconducting monolayer MoS2 with the high conductivity of graphene to build a 2D heterostructure capable of information storage. MoS2 acts as a channel in an intimate contact with graphene electrodes in a field-effect transistor geometry. Our prototypical all-2D transistor is further integrated with a multilayer graphene charge trapping layer into a device that can be operated as a nonv...
Herein we report the electrical transport properties of a series of ordered mesoporous ceria-zirconia (CexZr1-xO2, referred to as mp-CZO) thin films with both a cubic structure of (17 ± 2) nm diameter pores and nanocrystalline walls. Samples over the whole range of composition, including bare CeO2 and ZrO2, were fabricated by templating strategies using the large diblock copolymer KLE as the structure-directing agent. Both the nanoscale structure and the chemical composition of the mesoporous materials wer...
Shape-programmed nanofabrication: understanding the reactivity of dichalcogenide precursors.
Dialkyl and diaryl dichalcogenides are highly versatile and modular precursors for the synthesis of colloidal chalcogenide nanocrystals. We have used a series of commercially available dichalcogenide precursors to unveil the molecular basis for the outcome of nanocrystal preparations, more specifically, how precursor molecular structure and reactivity affect the final shape and size of II-VI semiconductor nanocrystals. Dichalcogenide precursors used were diallyl, dibenzyl, di-tert-butyl, diisopropyl, diethy...
Peak forces in high-resolution imaging of soft matter in liquid.
The maximum force exerted by the tip of a force microscope on the sample surface is a critical factor that determines the spatial resolution and the degree of invasiveness of the measurement, in particular, on soft materials. Here we determine the conditions needed to image soft matter in the 30-500 MPa range while applying very small forces. Imaging at sub-50 pN in the elastic regime can only be achieved under strict conditions in terms of force constant values (below 0.1 N/m) and free amplitudes (below 2...
We investigated the surface bonding and ordering of free-base porphine (2H-P), the parent compound of all porphyrins, on a smooth noble metal support. Our multitechnique investigation reveals a surprisingly rich and complex behavior, including intramolecular proton switching, repulsive intermolecular interactions, and density-driven phase transformations. For small concentrations, molecular-level observations using low-temperature scanning tunneling microscopy clearly show the operation of repulsive interac...
To develop structure-performance relationships for important catalysts, a detailed characterization of their morphology is essential. Using electron tomography, we determined in three dimensions the structure of Pt/zeolite Y bifunctional catalysts. Optimum experimental conditions enabled for the first time high-resolution 3D imaging of Pt particles as small as 1 nm located inside zeolite micropores. Semiautomated image analysis of 3D reconstructions provided an efficient study of numbers, size distributions...
Spontaneous self-assembly of silver nanoparticles into lamellar structured silver nanoleaves.
Uniform lamellar silver nanoleaves (AgNLs) were spontaneously assembled from 4 nm silver nanoparticles (AgNPs) with p-aminothiophenol (PATP) as mediator under mild shaking at room temperature. The compositions of the AgNLs were verified to be ∼1 nm Ag25 nanoclusters and PATP molecules in quinonoid model. The underlying assembly mechanism was systematically investigated and a two-step reaction process was proposed. First, the 4 nm AgNPs were quickly etched to ∼1 nm Ag25 nanoclusters by PATP in the form o...
Nitrogen-doped partially reduced graphene oxide rewritable nonvolatile memory.
As memory materials, two-dimensional (2D) carbon materials such as graphene oxide (GO)-based materials have attracted attention due to a variety of advantageous attributes, including their solution-processability and their potential for highly scalable device fabrication for transistor-based memory and cross-bar memory arrays. In spite of this, the use of GO-based materials has been limited, primarily due to uncontrollable oxygen functional groups. To induce the stable memory effect by ionic charges of a ne...
Self-assembly of light-harvesting crystalline nanosheets in aqueous media.
A methodology leading to facile self-assembly of crystalline aromatic arrays in dilute aqueous solutions would enable efficient fabrication and processing of organic photonic and electronic materials in water. In particular, soluble 2D crystalline nanosheets may mimic the properties of photoactive thin films and self-assembled monolayers, covering large areas with ordered nanometer-thick material. We designed such solution-phase arrays using hierarchical self-assembly of amphiphilic perylene diimides in aqu...
The influence of a CdSexS1-x interfacial alloyed layer on the photophysical properties of core/shell CdSe/CdS nanocrystal quantum dots (QDs) is investigated by comparing reference QDs with a sharp core/shell interface to alloyed structures with an intermediate CdSexS1-x layer at the core/shell interface. To fully realize the structural contrast, we have developed two novel synthetic approaches: a method for fast CdS-shell growth, which results in an abrupt core/shell boundary (no intentional or unintentiona...
Single-walled carbon nanotubes (SWCNTs) exhibit intrinsic fluorescence and strong optical absorption in the near-infrared (NIR) biological window (0.7-1.4 μm), rendering them ideal for in vivo imaging and photothermal therapy. Advances in SWCNT sorting have led to improved nanoelectronics and are promising for nanomedicine. To date, SWCNTs used in vivo consist of heterogeneous mixtures of nanotubes and only a small subset of chirality nanotubes fluoresces or heats under a NIR laser. Here, we demonstrate th...
Correlating structure, conductance, and mechanics of silver atomic-scale contacts.
We measure simultaneously force and conductance of Ag metal point-contacts under ambient conditions at room temperature. We observe the formation of contacts with a conductance close to 1 G0, the quantum of conductance, which can be attributed to a single-atom contact, similar to those formed by Au. We also find two additional conductance features at ∼0.4 G0 and ∼1.3 G0, which have been previously ascribed to contacts with oxygen contaminations. Here, using a conductance cross-correlation technique, we...
The influence of lattice strain on the oxygen exchange kinetics and diffusion in oxides was investigated on (100) epitaxial La1-xSrxCoO3-δ (LSC) thin films grown by pulsed laser deposition. Planar tensile and compressively strained LSC films were obtained on single-crystalline SrTiO3 and LaAlO3. (18)O isotope exchange depth profiling with ToF-SIMS was employed to simultaneously measure the tracer surface exchange coefficient k* and the tracer diffusion coefficient D* in the temperature range 280-475 °C. I...
Delaminated graphene at silicon carbide facets: atomic scale imaging and spectroscopy.
Atomic-resolution structural and spectroscopic characterization techniques (scanning transmission electron microscopy and electron energy loss spectroscopy) are combined with nanoscale electrical measurements (conductive atomic force microscopy) to study at the atomic scale the properties of graphene grown epitaxially through the controlled graphitization of a hexagonal SiC(0001) substrate by high temperature annealing. This growth technique is known to result in a pronounced electron-doping (∼10(13) cm(-...
Laser welding of ruptured intestinal tissue using plasmonic polypeptide nanocomposite solders.
Approximately 1.5 million people suffer from colorectal cancer and inflammatory bowel disease in the United States. Occurrence of leakage following standard surgical anastomosis in intestinal and colorectal surgery is common and can cause infection leading to life-threatening consequences. In this report, we demonstrate that plasmonic nanocomposites, generated from elastin-like polypeptides (ELPs) cross-linked with gold nanorods, can be used to weld ruptured intestinal tissue upon exposure to near-infrared...
Optical nanoantennas for multiband surface-enhanced infrared and Raman spectroscopy.
In this article we show that linear nanoantennas can be used as shared substrates for surface-enhanced Raman and infrared spectroscopy (SERS and SEIRS, respectively). This is done by engineering the plasmonic properties of the nanoantennas, so to make them resonant in both the visible (transversal resonance) and the infrared (longitudinal resonance), and by rotating the excitation field polarization to selectively take advantage of each resonance and achieve SERS and SEIRS on the same nanoantennas. As a pro...
Biomimetic cryptic site surfaces for reversible chemo- and cyto-mechanoresponsive substrates.
Chemo-mechanotransduction, the way by which mechanical forces are transformed into chemical signals, plays a fundamental role in many biological processes. The first step of mechanotransduction often relies on exposure, under stretching, of cryptic sites buried in adhesion proteins. Likewise, here we report the first example of synthetic surfaces allowing for specific and fully reversible adhesion of proteins or cells promoted by mechanical action. Silicone sheets are first plasma treated and then functiona...
