Controlled synthesis of double- and multiwall silver nanotubes with template organogel from a bolaamphiphile

Double- and multiwall silver nanotubes were synthesized by using the uniform low-molecular-mass organogel nanotubes self-assembled from an L-glutamic-acid-based bolaamphiphile, N,N-eicosanedioyl-di-L-glutamic acid (EDGA). The EDGA could gel a mixed water/ethanol solvent and form helical nanotubes. When the gel thus formed was mixed with AgNO3 in water/ethanol, the silver(I) cations could be coordinated with both the inner and outer surfaces of the EDGA nanotubes. The reduction of the silver cation under the photoirradiation yielded double-wall silver nanotubes, where two silver layers were separated by one EDGA layer. Elongations of the reduction time of the mixed gels and AgNO3 in the solution lead to the formation of three-, four-, and five-wall silver nanotubes. In these multiwall silver nanotubes, each wall was separated at a distance of about 2.7 nm, which was just the molecular length of the bolaamphiphile. It was suggested that the dissolved EDGA molecules and excess Ag(I) cations were further assembled onto the surface of the formed double-wall silver nanotubes and, as a consequence, the photoreduction caused the formation of the third-wall silver nanotubes. The multiwall silver nanotubes were further formed in a similar way. The factors affecting the formation of the silver wall nanotubes such as the relative amount of AgNO3 to EDGA and the synthetic conditions were discussed.     

Large-scale synthesis of silver nanowires and platinum nanotubes

Silver nanowires have been synthesized by ethylene glycol reduction of silver nitrate with the assistance of polyvinyl pyrrolidone and sodium sulfide in a large scale. By adjusting the reaction temperature and Na₂S content, silver nanowires with lengths up to 3?4 μm can be achieved in high yield. Scanning electron microscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected areas electron diffraction (SAED), and X-ray diffraction (XRD) have been employed to characterize silver nanowires. Platinum nanotubes with length about 3 μm can be prepared using as-prepared silver nanowires as sacrificial templates. Platinum nanotubes were characterized by TEM, SAED, and HRTEM.     

Redox-induced synthesis and encapsulation of metal nanoparticles in shell-cross-linked organometallic nanotubes

A new approach to encapsulate silver nanoparticles inside block copolymer nanotubes is reported and involves an in situ redox reaction between a polyferrocenylsilane (PFS) inner wall and silver ions. Partial preoxidation of the PFS domains was found to be a key step for the efficient formation of one-dimensional arrays of silver nanoparticles confined within the nanotubes.     

Modification of multi-wall carbon nanotube surfaces with poly(amidoamine) dendrons: synthesis and metal templating

Hydroxyl functional poly(amidoamine) dendron wedges have been reacted with the surface of multi-walled carbon nanotubes and used for templating silver nanoparticles.     

Coinage metal (4, 4) nanotubes, simulated by first-principles calculations

The structural stability of coinage metal nanotubes with a square cross-section has been investigated by the first-principles numerical simulations. In addition to the reported (4, 4) silver tube, it is found that the hollow (4, 4) copper and gold nanotubes can also be formed by applying an appropriate stress to an 8(A)/8(B) fcc wire. The stability of these coinage metal (4, 4) nanotubes, formed by tip-stretching the wires, has been explained by a local minimum in the string tension variation with their tube lengths. Interestingly, we have explained why a low-stress stretching is needed to obtain the (4, 4) Cu tube in contrast to a higher one for both the (4, 4) Ag and Au tubes due to the larger stiffness coefficient of copper than those of silver and gold, which could be proved by future experiments.     

One‐Step Preparation of Antimicrobial Polyrhodanine Nanotubes with Silver Nanoparticles

A simple synthetic method has been developed for the fabrication of antimicrobial polyrhodanine nanotubes with silver nanoparticles. Rhodanine monomer first forms one‐dimensional complexes with silver ions due to coordinative interactions and consecutively reduces the silver ions during chemical‐oxidation polymerization. The polymerization procedure is analyzed by transmission electron microscopy and scanning electron microscopy in situ. The synthesized silver nanoparticles/polyrhodanine nanotubes are applied as an antimicrobial agent against Gram‐negative bacteria, E. coli and Gram‐positive bacteria, S. aureus. The antimicrobial tests demonstrate that the silver/polyrhodanine nanotubes have superior antimicrobial properties to silver nanoparticles and rhodanine monomer.

     

Silver telluride nanotubes prepared by the hydrothermal method

Silver telluride nanotubes have been prepared by the hydrothermal process without a template or a surfactant. The as-prepared sample was characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectra, and Raman spectra. The structural phase transition of the sample was observed. A rolling-up mechanism is proposed to explain the formation of the silver telluride nanotubes based on the inherent crystal structure of low-temperature beta-Ag2Te. Raman spectra analysis revealed an interesting Raman scattering enhancement phenomenon.     

Synthesis and Characterization of Silver–Platinum Bimetallic Nanowires and Platinum Nanotubes

A galvanic replacement reaction was used to prepare silver–platinum bimetallic nanowires and platinum nanotubes. Silver nanowires, prepared by boiling aqueous silver nitrate with sodium citrate in the presence of small amount of sodium hydroxide, were used as the sacrificial template in the galvanic reaction to prepare silver–platinum bimetallic nanowires and ultimately hollow platinum nanotubes. The resulting nanomaterials are stable and can be isolated without core aggregation or decomposition. These new materials have been characterized by transmission electron microscopy, energy dispersive X-ray analysis, and inductively coupled plasma atomic emission spectroscopy.     

Ag‐CNT Architectures for Attomolar Dopamine Detection and 100‐Fold Fluorescence Enhancements with Cellphone‐Based Surface Plasmon‐Coupled Emission Platform

We report cellphone‐based detection of dopamine with attomolar sensitivity in clinical samples with the use of a surface plasmon‐coupled emission (SPCE) platform. To this end, silver‐coated carbon nanotubes were used as spacer and cavity materials on SPCE substrates to obtain up to 100‐fold fluorescence enhancements. The presence of silver on the carbon nanotubes helped to overcome fluorescence quenching arising due to π–π interactions between the carbon nanotube and rhodamine 6G. The competing adsorption of dopamine versus rhodamine 6G on graphene oxide was utilized to develop this sensing platform.     

Silver-coated TiO2 nanostructured anode materials for lithium ion batteries

Anatase TiO₂ nanoribbons/nanotubes (TiO₂-NRTs) have been synthesised successfully via a reflux method followed by drying in a vacuum oven, and then, silver-coated TiO₂ NRTs (Ag/TiO₂-NRTs) were prepared by coating silver particles onto the TiO₂-NRTs surface by the traditional silver mirror reaction. The physical properties of the synthesised products were examined in detail using X-ray diffraction, field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy, respectively. The results indicated that the Ag nanoparticles were uniformly deposited on the surface of the TiO₂ nanoribbons/nanotubes. The electrochemical properties were investigated by a variety of techniques. The rate capability and cycle durability for the Ag/TiO₂-NRTs were improved compared with TiO₂-NRTs. It is speculated that the Ag-coated TiO₂ nanoribbons/nanotubes are an effective anode candidate for lithium ion batteries.     

A facile route to fabrication of inorganic-small organic molecule cable-like nanocomposite arrays

A novel and facile method is reported for the preparation of silver iodide-small organic molecule (SOM) cable-like nanocomposites arrays, which involved first the fabrication of SOM nanotubes inside an anodic aluminium oxide (AAO) membrane, and then using the SOM nanotubes in AAO as secondary template to prepare the AgI nanowires in aqueous solution at room temperature.     

单壁碳纳米管在不同材质基片银膜上的表面增强拉曼光谱

在玻璃、白宝石和石英基片上,利用化学沉积法和溶胶法制备了纳米结构活性银膜,系统地研究了两种不同方法制备的单壁碳纳米管(SWNT)的表面增强拉曼光谱(SERS)的G带和D带.同一样品的G带,在不同基片上的峰移量不同,在白宝石基片上移动更大,峰强更高,可以更敏感地反映SERS效应.D带的峰形随基片不同而改变.金属性管的含量较高的样品,其D带光谱的峰移较半导体性管含量较高的样品更显著,表明金属性碳纳米管与SERS活性银膜的界面相互作用更强.     

Preparation and electrochemical properties of Ag-modified TiO2 nanotube anode material for lithium–ion battery

TiO₂ nanotubes prepared by using a hydrothermal process were firstly coated with silver nanoparticles as the anode materials for lithium–ion batteries by the traditional silver mirror reaction. The physical properties of the as-synthesized samples were investigated by X-ray diffraction and transmission electron microscopic. The as-prepared samples were used as negative materials for lithium–ion battery, whose charge–discharge properties, cyclic voltammetry, electrochemical impedance spectroscopy and cycle performance were examined in detail. The results showed that the Ag additive decreased the polarization of anode, and marvelously improved the high-rate discharge capacity and cycling stability of TiO₂ nanotubes.     

Efficient silver modification of TiO2 nanotubes with enhanced photocatalytic activity

In this paper, Ag(CH₃NH₂)₂⁺, Ag(NH₃)₂⁺ and Ag⁺ with different radii have been used as silver sources to find out the distribution of Ag ions on the H-TNT surface, which is critical to the final performance. The influence of this distribution on visible photocatalytic activity is further studied. The results indicate that, when Ag⁺ used as silver source with low concentration, these small sized silver ions mainly distribute on interlayer spacing of H-TNT. After heat-treatment and photo-reduction, the generated silver nanoparticles uniformly embed in the anatase TiO₂ nanotube walls, and bring large interfacial area between Ag particles and TiO₂ nanotubes. The separation effect of photogenerated electron-hole pair in TiO₂ is enhanced by Ag particles, and achieves the best at 0.15 g/L, much higher than P25, TiO₂/0, Ag-N@TiO₂ and Ag-C-N@TiO₂. This paper provides new ideas for the modification of TiO₂ nanotubes.     

银溶胶诱导多壁碳纳米管非共价表面修饰

利用银溶胶活化诱导淀粉螺旋结构实现了多壁碳纳米管非共价表面修饰. 实验结果表明, 淀粉非共价表面修饰的多壁碳纳米管在水中容易分散, 扫描电镜分析表明, 经银溶胶处理的多壁碳纳米管被单根分散在银溶胶溶液中. 酶解试验、IR和EDS分析表明, 碳纳米管表面修饰了一层淀粉.     

Experimental analysis of heat transfer behavior of silver,MWCNT and hybrid (silver +MWCNT) nanofluids in a laminar tubular flow

Journal of Thermal Analysis and Calorimetry - Experimental investigations were carried out in order to study the heat transfer performance of silver (Ag), multiwalled carbon nanotubes (MWCNT) and...     

Entrap and release of Phe–Phe nanotubes in sol–gel derived silicate matrix: study through nanosilver interaction

After the discovery of the ability of dipeptide self-assembly, numerous research activities have been reported on Phe–Phe dipeptide based nano-materials. However, entrapping peptide nanotubes in a silicate matrix has not been carefully studied. This paper reports on self-assembled Phe–Phe nanotubes entrapped in a silicate matrix derived by a simple, and modified acid mediated sol–gel approach. Here, interaction of silver nanoparticles with regained nanotubes from the silicate matrix is reported. Mass spectrometry data showed the self-assembly of peptide monomers. Scanning electron microscopy and transmission electron microscopy studies have been used to examine the shapes and sizes of the nano-structures, and the results provide a promising method for trapping peptide based nanotubes. UV–Visible spectra suggest that there are some effects of silicate environment around Phe–Phe NTs on its absorbance. Density functional calculations showed the probable type of interaction between peptide and Ag atoms. This study can be useful for future applications, which are based on immobilization strategy for drug carrying and sensing.     

Reduction of silver nitrate by polyaniline nanotubes to produce silver-polyaniline composites

Polyaniline (PANI) nanotubes were prepared by oxidation of aniline in 0.4 M acetic acid. They were subsequently used as a reductant of silver nitrate in 1 M nitric acid, water or 1 M ammonium hydroxide at various molar ratios of silver nitrate to PANI. The resulting PANI-silver composites contained silver nanoparticles of 40–60 nm size along with macroscopic silver flakes. Under these experimental conditions, silver was always produced outside the PANI nanotubes. Changes in the molecular structure of PANI were analyzed by FTIR spectroscopy. Silver content in the composites was determined as a residue by thermogravimetric analysis, and confirmed by density measurements. The highest conductivity of a composite, 68.5 S cm⁻¹, was obtained at the nitrate to PANI molar ratio of 0.67 in water. Also, the best reaction yield was obtained in water. Reductions performed in an acidic medium gave products with conductivity of 10⁻⁴–10⁻² S cm⁻¹, whereas the reaction in alkaline solution yielded non-conducting products.     

A new surface-enhanced Raman scattering system for carbon nanotubes

A new surface-enhanced Raman scattering (SERS) system of carbon nanotubes (CNTs) is reported for the first time. According to the remarkable mechanical property, CNTs were grinded on a sheet of silver directly. Thus rough silver surface was obtained, at the same time, the CNTs attached to the rough silver surface. High quality SERS spectra were obtained from CNTs attached to the rough silver surface. Because there were no solvents affecting the SERS of CNTs, the dependability of the result is improved. The theory and experiment results indicate that this is an accurate and practicable method for SERS study of CNTs.     

Electrocrystallized Ag nanoparticle on functional multi-walled carbon nanotube surfaces for hydrazine oxidation

4-Aminobenzoic acid was covalently grafted on multi-walled carbon nanotubes (MWNTs) by amine cation radical formation in the electrooxidation process of the amino-containing compound. Then, silver (Ag) nanoparticles were electrocrystallized on 4-aminobenzoic acid monolayer-grafted MWNTs by a potential-step method. The structure and nature of the resulting Ag/MWNT composites were characterized by transmission electron microscopy and X-ray diffraction. The electrocatalytic properties of the Ag/MWNT electrode for hydrazine oxidation have been investigated by cyclic voltammetry, high electrocatalytic activity of the Ag/MWNT electrode can be observed. This may be attributed to the small particle size of the silver particles. The results imply that the Ag/MWNT composites have a good application potential in fuel cells.