A novel method for the synthesis of Au nanoparticles incorporated amorphous hydrogenated carbon films

In this communication we report a novel electrochemical route for the preparation of Au nanoparticles incorporated a-C:H films on single crystal silicon substrates by choosing methanol as carbon source and Au nanoparticles as dopant. The morphology, composition and structure of the film have been investigated and the results show that the film obtained in our method is a hydrogenated diamond-like carbon film and zero-valence Au nanoparticles are stable and well-dispersed into the amorphous carbon matrix with unchanged size. It is simplified to achieve the co-deposition of carbon and metal by using metal nanoparticles rather than the metal salt solution as the dopant. The incorporation of Au nanoparticles in the carbon matrix can drastically decrease the resistivity and convert a-C:H films from insulator to semiconductor easily. The growth mechanisms of the Au-DLC films are also discussed.     

含金属纳米粒子的层层自组装及单壁碳纳米管的催化生长

利用层间的静电吸附作用，重氮树脂和不同种类的含金属纳米粒子被依次吸附到硅片表面形成层层自组装膜。通过改变自组装膜的层数可以控制纳米粒子在表面吸附的量，同时利用重氮树脂的光敏特性可以实现纳米粒子在表面的图案化排布。以这些纳米粒子为催化剂，研究了单壁碳纳米管在硅片表面的化学气相沉积生长。     

Metal/metal sulfide functionalized single-walled carbon nanotubes: FTO-free counter electrodes for dye sensitized solar cells

The use of single-walled carbon nanotubes (CNT) thin films to replace conventional fluorine-doped tin oxide (FTO) and both FTO and platinum (Pt) as the counter electrode in dye sensitized solar cells (DSSC) requires surface modification due to high sheet resistance and charge transfer resistance. In this paper, we report a simple, solution-based method of preparing FTO-free counter electrodes based on metal (Pt) or metal sulfide (Co(8.4)S(8), Ni(3)S(2)) nanoparticles/CNT composite films to improve device performance. Based on electrochemical studies, the relative catalytic activity of the composite films was Pt > Co(8.4)S(8) > Ni(3)S(2). We achieved a maximum efficiency of 3.76% for the device with an FTO-free counter electrode (Pt/CNT). The device with an FTO- and Pt-free (CoS/CNT) counter electrode gives 3.13% efficiency.     

金属和半导体纳米微粒薄膜的制备

由于金属、半导体纳米微粒在光物理、光化学、光催化等方面具有突出的性能,因此如何将金属、半导体纳米微粒通过某些方式构建成某些薄膜材料,对实现纳米微粒在分子器件和光电器件方面的应用具有重要的意义.本文以制备方法为主线,介绍了几种构建金属、半导体纳米微粒薄膜的基本方法,对其中一些重要的问题进行了比较详细的讨论.     

Structurally Organized Nanocomposites in the Catalysis of Chlorohydrocarbon Reactions

Catalysis by closely packed metal films containing monodispersed nanocluster ensembles was considered using the reactions of chlorinated hydrocarbons as an example; these reactions include a step of electron transfer from a catalyst to a reactant. A new laser electrodispersion technique was used for preparing films that consisted of spherical copper grains 5 nm in size coated with thin (0.7 nm) layers of copper(I) oxide with different particle packing densities on the surface of thermally oxidized silicon. A comparison of the catalytic activity of films with varied packing density in media with different permittivities allowed us to assume that the observed maximum activity of closely packed films was associated with the appearance of charged grains in the ensembles of interacting nanoparticles due to the thermal fluctuations of electrons between closely spaced grains.     

Self-assembled metal colloid films: two approaches for preparing new SERS active substrates

In this paper, we propose two new approaches for preparing active substrates for surface-enhanced Raman scattering (SERS). In the first approach (method 1), one transfers AgI nanoparticles capped by negatively charged mercaptoacetic acid from a AgI colloid solution onto a quartz slide and then deoxidizes AgI to Ag nanoparticles on the substrate. The second approach (method 2) deoxidizes AgI to Ag nanoparticles in a colloid solution and then transfers the Ag nanoparticles capped by negatively charged mercaptoacetic acid onto a quartz slide. By transfer of the AgI/Ag nanoparticles from the colloid solutions to the solid substrates, the problem of instability of the colloid solutions can largely be overcome. The films thus prepared by both approaches retain the merits of metal colloid solutions while they discharge their shortcomings. Accordingly, the obtained Ag particle films are very suitable as SERS active substrates. SERS active substrates with different coverages can be formed in a layer-by-layer electrostatic assembly by exposing positively charged surfaces to the colloid solutions containing oppositely charged AgI/Ag nanoparticles. The SERS active substrates fabricated by the two novel methods have been characterized by means of atomic force microscopy (AFM) and ultraviolet-visible (UV-vis) spectroscopy. The results of AFM and UV-vis spectroscopy show that the Ag nanoparticles grow with the increase in the number of coverage and that most of them remain isolated even at high coverages. Consequently, the surface optical properties are dominated by the absorption due to the isolated Ag nanoparticles. The relationship between SERS intensity and surface morphology of the new active substrates has been investigated for Rhodamine 6G (R6G) adsorbed on them. It has been found that the SERS enhancement depends on the size and aggregation of the Ag particles on the substrates. Especially, we can obtain a stronger SERS signal from the substrate prepared by method 1, implying that for the metal nanoparticles capped with stabilizer molecules such as mercaptoacetic acid, the in situ deoxidization in the film is of great use in preparing SERS active substrates. Furthermore, we have found that the addition of Cl- into the AgI colloid solution changes the surface morphology of the SERS active substrates and favors stronger SERS enhancement.     

Infrared reflection–absorption properties of platinum nanoparticle films on metal electrode substrates: control of anomalous optical effects

A simple method is described for preparing ultrathin films of carbon-supported platinum nanoparticles on gold and other substrates for examination by electrochemical infrared reflection–absorption spectroscopy (EC-IRAS) in which the anomalous “anti-absorbance” properties commonly observed for metal particle arrays can be minimized as well as controlled. The tactic involves physical deposition as an aqueous suspension, followed by drying and thorough rinsing. The Pt monolayer-level films prepared by this means exhibit largely positive unipolar absorbance bands for CO adlayers, whereas an anomalous inverted band component appears for thicker films, especially those featuring high Pt nanoparticle loadings. These findings demonstrate the value of the film preparation tactic for exploring the electrocatalytic properties of C/Pt materials by using combined electrochemical and EC-IRAS measurements.     

CO2-expanded liquid deposition of ligand-stabilized nanoparticles as uniform, wide-area nanoparticle films

Deposition of nanoparticles into uniform, wide-area thin films using CO(2) as an antisolvent is presented. Ligand-stabilized silver particles are controllably precipitated from organic solvents by pressurizing and expanding the solution with carbon dioxide. Subsequent addition of carbon dioxide as a dense supercritical fluid provides for removal of the organic solvent while avoiding the surface tensions common to evaporating solvents that are detrimental to nanoscale assemblies and structures. This brand new CO(2)-expanded liquid particle deposition technique allows for the targeted deposition of particles and results in more uniform and lower defect metal nanoparticle thin films than are provided by conventional solvent evaporation techniques.     

In situ Synthesis of Metal Nanoparticle Embedded Free Standing Multifunctional PDMS Films

We demonstrate a simple one‐step method for synthesizing noble metal nanoparticle embedded free standing polydimethylsiloxane (PDMS) composite films. The process involves preparing a homogenous mixture of metal salt (silver, gold and platinum), silicone elastomer and the curing agent (hardener) followed by curing. During the curing process, the hardener crosslinks the elastomer and simultaneously reduces the metal salt to form nanoparticles. This in situ method avoids the use of any external reducing agent/stabilizing agent and leads to a uniform distribution of nanoparticles in the PDMS matrix. The films were characterized using UV‐Vis spectroscopy, transmission electron microscopy and X‐ray photoemission spectroscopy. The nanoparticle‐PDMS films have a higher Young's modulus than pure PDMS films and also show enhanced antibacterial properties. The metal nanoparticle‐PDMS films could be used for a number of applications such as for catalysis, optical and biomedical devices and gas separation membranes.

     

A Honeycomb-Like Bulk Superstructure of Carbon Nanosheets for Electrocatalysis and Energy Storage

Superstructures have attracted extensive attention because of their potential applications in materials science and biology. Herein, we fabricate the first centimeter-sized porous superstructure of carbon nanosheets (SCNS) by using metal–organic framework nanoparticles as a template and polyvinylpyrrolidone as an additional carbon source. The SCNS shows a honeycomb-like morphology with wall-sharing carbon cages, in each cavity of which a porous carbon sphere is encapsulated. A single piece of SCNS is directly used as the electrode for a two-electrode symmetrical supercapacitor cell without any binders and supports, benefiting from its advantage in ultra-large geometric size, and the Fe-immobilized SCNS exhibits excellent catalytic performances for oxygen reduction reaction and in a Zn–air battery. This synthetic strategy presents a facile approach for preparing functional SCNS at centimetric scale with controllable morphologies and compositions favoring the fabrication of energy devices.     

A general route to prepare one- and three-dimensional carbon nanotube/metal nanoparticle composite nanostructures

Adsorption of polyethyleneimine (PEI)-metal ion complexes onto the surfaces of carbon nanotubes (CNTs) and subsequent reduction of the metal ion leads to the fabrication of one-dimensional CNT/metal nanoparticle (CNT/M NP) heterogeneous nanostructures. Alternating adsorption of PEI-metal ion complexes and CNTs on substrates results in the formation of multilayered CNT films. After exposing the films to NaBH4, three-dimensional CNT composite films embedded with metal nanoparticles (NPs) are obtained. UV-visible spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy are used to characterize the film assembly. The resulting (CNT/M NP)n films inherit the properties from both the metal NPs and CNTs that exhibit unique performance in surface-enhanced Raman scattering (SERS) and electrocatalytic activities to the reduction of O2; as a result, they are more attractive compared to (CNT/polyelectrolyte)n and (NP/polyelectrolyte)n films because of their multifunctionality.     

Electrodeposition and characterization of Pd nanoparticles doped amorphous hydrogenated carbon films

Palladium (0) nanoparticles incorporated hydrogenated amorphous carbon (Pd/a-C:H) films were synthesized on single crystal silicon (100) substrates by electrochemical deposition route using methanol and camphor as carbon source, and Pd nanoparticles as dopant. The characterization results indicate that Pd nanocrystalline particles with diameter in the range of 1–5 nm dispersed in the amorphous carbon matrix. Compared with pure a-C:H films, the introduction of Pd nanoparticles didn't change the structure of carbon films. At the end, the growth mechanism of the Pd/a-C:H composite films was discussed.     

A general solution-phase approach to oriented nanostructured films of metal chalcogenides on metal foils: the case of nickel sulfide

Oriented films of nickel sulfide nanostructures, ranging from hierarchical dendrites to nanobelts and nanorods, were hydrothermally grown on Ni foils. This approach has proven to be a general method for preparing nanostructured metal chalcogenides films on corresponding metal foils.     

Poly(methyl methacrylate) composites with size‐selected silver nanoparticles fabricated using cluster beam technique

An embedment of metal nanoparticles of well‐defined sizes in thin polymer films is of significant interest for a number of practical applications, in particular, for preparing materials with tunable plasmonic properties. In this article, we present a fabrication route for metal–polymer composites based on cluster beam technique allowing the formation of monocrystalline size‐selected silver nanoparticles with a ±5–7% precision of diameter and controllable embedment into poly (methyl methacrylate). It is shown that the soft‐landed silver clusters preserve almost spherical shape with a slight tendency to flattening upon impact. By controlling the polymer hardness (from viscous to soft state) prior the cluster deposition and annealing conditions after the deposition the degree of immersion of the nanoparticles into polymer can be tuned, thus, making it possible to create composites with either particles partly or fully embedded into the film. Good size selection and rather homogeneous dispersion of nanoparticles in the thin polymer film lead to excellent plasmonic properties characterized by the narrow band and high quality factor of localized surface plasmon resonance. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1152–1159     

Reactivity of hydrogen with solid-state films of alkylamine- and tetraoctylammonium bromide-stabilized Pd, PdAg, and PdAu nanoparticles for sensing and catalysis applications

Hydrogen gas spontaneously adsorbs to Pd metal as atomic hydrogen and diffuses into the lattice to form PdHx. We previously showed that films of hexanethiolate-coated Pd monolayer-protected clusters (MPCs) do not readily react with H2 due to the strong chemical bonding of the thiolate to the Pd, which inhibits the reaction. Consequently, these films require ozone or heat treatment for reactivity to occur, which is inconvenient for sensing or catalysis applications. In this report, we describe the reactivity between H2 and solid-state films of alkylamine-coated Pd, PdAg (10:1), and PdAu (10:1) MPCs and films of tetraoctylammonium bromide (TOABr)-stabilized Pd and PdAg (10:1) nanoparticles as determined by changes in film conductivity. Our data show that Pd nanoparticles coated with these more weakly coordinated amine or ammonium groups readily react with H2 without any need for ozone or heat treatment. The conductivity of films of octylamine (C8NH2)- or dodecylamine (C12NH2)-coated Pd, PdAg, and PdAu MPCs increases irreversibly upon initial exposure to 100% H2 to varying degrees and with different reaction kinetics and then exhibits stable, reversible changes in the presence of H2 concentrations ranging from 9.6 to 0.08%. The behavior upon initial exposure to H2 (conditioning) and the direction and magnitude of the reversible conductivity changes depend on the alkyl chainlength and alloy composition. Films of TOABr-coated Pd and PdAg nanoparticles show stable, reversible increases in conductivity in the presence of H2 concentrations from 9.6 down to 0.11% without conditioning. Surface FTIR spectroscopy and atomic force microscopy (AFM) provide information about the organic monolayer and film morphology, respectively, following reactivity with H2. This work demonstrates a simple approach toward preparing films of chemically synthesized Pd-containing nanoparticles with controlled reactivity to H2 for sensing and catalysis applications.     

Preparation and electrochemical behaviors of platinum nanoparticles impregnated on binary carbon supports as catalyst electrodes of direct methanol fuel cells

Binary carbon-supported platinum (Pt) nanoparticles were prepared by a chemical reduction method of Pt precursor on two types of carbon materials such as carbon blacks (CBs) and graphite nanofibers (GNFs). Average sizes and loading levels of Pt metal particles were dependent on a mixing ratio of two carbon materials. The highest electroactivity for methanol oxidation was obtained by preparing the binary carbon supports consisting of GNFs and CBs with a weight ratio of 30:70. Furthermore, with an increase of GNFs content from 0% to 30%, a charge-transfer resistance changed from 19 Ohm cm² to 11 Ohm cm². The change of electroactivity or the resistance of catalyst electrodes was attributed to the changes of specific surface area and morphological changes of carbon-supported catalyst electrodes by controlling the mixing ratio of GNFs and CBs.     

Preparation and electrochemical polymerization of new multifunctional pyrrolethiolate-stabilized gold and palladium nanoparticles

New pyrrolylalkanethiolate-stabilized gold and palladium nanoparticles have been prepared: electrochemical polymerization of their metal nanoparticles and their TEMPO-derivatized metal nanoparticles gave the remarkably stable poly(pyrrole metal nanoparticle) films on metal electrodes.     

Synthesis of silver and copper nanoparticle containing a-C:Hby ion irradiation of polymers

One of the many applications of diamond like carbon (DLC) is the biocompatible coating of medical tools and implants. The most recent field of interest concerns the generation of antimicrobial activity in combination with the excellent wear resistance and biocompatibility of DLC. As has already been shown for polymers, nanoparticles of silver or copper within a carbonacious matrix have a bactericidal effect.In this work we describe a new technique to produce amorphous hydrogenated carbon films (a-C:H), which contain nanometer sized clusters of silver or copper. The hybrid deposition process is based on sol–gel synthesis of polymer films and subsequent ion-induced densification and cross-linking to form a-C:H. By thermal or UV-induced reduction of metal salts in polymer solution, colloidal metal particles are produced. In this way polymer films, already containing noble metal nanoclusters, can be deposited in a wet chemical step. Upon sol–gel deposition, the polymer is subjected to ion irradiation. Based on earlier results, the influence of ion energy on chemical and mechanical properties, as well as bonding structure is investigated. Special attention is also dedicated to ion-induced diffusion and growth as well as oxidation effects.     

Layer-by-layer immobilization of carbon dots fluorescent nanomaterials on single optical fiber

We report within this paper the development of a fiber-optic based sensor for Hg(II) ions. Fluorescent carbon nanoparticles were synthesized by laser ablation and functionalized with PEG₂₀₀ and N-acetyl-l-cysteine so they can be anionic in nature. This characteristic facilitated their deposition by the layer-by-layer assembly method into thin alternating films along with a cationic polyelectrolyte, poly(ethyleneimine). Such films could be immobilized onto the tip of a glass optical fiber, allowing the construction of an optical fluorescence sensor. When immobilized on the fiber-optic tip, the resultant sensor was capable of selectively detecting sub-micromolar concentrations of Hg(II) with an increased sensitivity compared to carbon dot solutions. The fluorescence of the carbon dots was quenched by up to 44% by Hg(II) ions and interference from other metal ions was minimal.     

Controlled growth of mesostructured crystalline iron oxide nanowires and Fe-filled carbon nanotube arrays templated by mesoporous silica SBA-16 film

The three-dimensional (3D) accessible pore structures (Imm space groups) of continuous mesoporous silica SBA-16 thin films have been prepared by a dip-coating technique in nonaqueous media under acidic conditions on indium-tin oxide glass (ITO). The films are oriented with the (111) crystal plane perpendicular to the surface of the film. On one hand, deposition of iron metal into the mesopores of SBA-16 films was achieved by using an electrochemical method. The Fe2O3 nanowire arrays were synthesized. The crystalline structures of porous Fe2O3 nanowires and nanorods were studied via TEM, SEM, and XRD. On the other hand, a small amount of Fe was deposited into the pores of the SBA-16 thin film as a catalyst, and carbon nanotube arrays formed inside the pores of SBA-16 film were fabricated by catalytic decomposition of acetylene at 700 degrees C. The second-order template synthesis method for preparing the ordered array of carbon nanotubes filled with Fe has been used. The carbon nanotubes are very uniform in diameter and length and are aligned vertically with respect to the SBA-16 film.